KR20230045736A - A method and apparatus for controlling a robot using feedback from a laser tracker - Google Patents

Abstract

In accordance with one embodiment of the present invention, provided is technology for controlling a robot such that an error of a processing path for an object to be processed can be easily corrected, in a processing process using a robot. In accordance with an embodiment of the present invention, a robot control method using laser tracker feedback, includes: a first step in a laser tracker is coupled to a robot to radiate a laser to a processing part provided with a tool, thereby measuring an actual position and an actual direction of a tool, which are a position and a direction in real time; a second step in which a reference processing path, which is a processing path of the tool preset in accordance with an object to be processed, is divided into a plurality of straight lines, and a reference position and a reference direction, which are a position and a direction of the tool on the reference processing path, are set; a third step in which a contour reference position which is a position of the tool with a position error corrected is derived by using two vertical connection lines connecting the actual position with each of two straight lines, passing through the nearest reference position which is a reference position nearest to the actual position, among the plurality of straight lines; a fourth step in which a contour reference direction which is a direction of the tool with a direction error corrected is derived by using the reference direction and the actual direction on the nearest reference position; and a fifth step in which as the robot is controlled with the contour reference position and the contour reference direction, the position and the direction of the tool are controlled.

Description

Robot control method and apparatus using laser tracker feedback {A METHOD AND APPARATUS FOR CONTROLLING A ROBOT USING FEEDBACK FROM A LASER TRACKER}

The present invention relates to a method and apparatus for controlling a robot using laser tracker feedback, and more particularly, to a technology for controlling a robot so that an error correction of a processing path for a processing target is easily performed in a processing process using a robot. will be.

In recent years, manufacturing systems using a plurality of robots are increasing, and in the production of products such as automobiles and aircraft, demands for improvement of automatic manufacturing efficiency and increase in processing precision using robots are continuously increasing.

When machining is performed using a robot, machining errors occur due to rigidity and kinematic factors of the robot. However, in the prior art robot control device, it was not easy to precisely measure the machining errors. In the technology, in order to improve the precision of machining errors, a method of reducing machining errors of the robot by collecting feedback on robot machining using a plurality of sensors and analyzing this information has been used, but this method is There is a problem that the developed control algorithm can be applied only to some open type robot controllers.

In Korean Patent Publication No. 10-2015-0070370 (Title of Invention: Method for Inline Calibration of Industrial Robot, Calibration System for Performing the Method, and Industrial Robot Including the Calibration System), at least three rays At least one generated using at least one light source 7 rigidly connected to the distal end 6 of the robotic arm 3 and adapted to determine the position of a light beam impinging on the sensor in a two-dimensional plane. The optical position sensor (12) of the robot arm (3) is configured so that at least some of the light rays generated by the at least one light source (7) at a predefined calibration site of the distal end (6) of the robotic arm (3) ) or positioned in a fixed location relative to the base part 2 of the robot to influence at least one of the sensors 12.

Republic of Korea Patent Publication No. 10-2015-0070370

An object of the present invention to solve the above problems is to control a robot so that an error correction of a machining path for a machining target is easily performed in a machining process using a robot.

And, an object of the present invention is to perform the above-described control for a robot while minimizing an additional separate device or complicated calculation.

The technical problem to be achieved by the present invention is not limited to the above-mentioned technical problem, and other technical problems not mentioned can be clearly understood by those skilled in the art from the description below. There will be.

The configuration of the present invention for achieving the above object is a first step of measuring the real position and direction, which is the real-time position and direction of the tool, by irradiating a laser to a processing unit having a tool in which a laser tracker is coupled to a robot ; A second step of dividing a reference machining path, which is a machining path of the tool previously set according to a machining target, into a plurality of straight lines, and setting a reference position and direction, which are the position and direction of the tool, on the reference machining path; The position where the position error of the tool is corrected using two straight lines each passing through the nearest reference position, which is the reference position closest to the actual position among the plurality of straight lines, and two vertical connecting lines vertically connecting the actual position. a third step of deriving the reference position of the contour; a fourth step of deriving a contour reference direction, which is a direction obtained by correcting a direction error of the tool, using the reference direction and the actual direction at the nearest reference position; and a fifth step of controlling the position and direction of the tool by controlling the robot using the contour reference position and the contour reference direction.

In an embodiment of the present invention, in the second step, the plurality of straight lines may be formed by dividing the reference machining path by an interpolator.

In an embodiment of the present invention, in the third step, the two straight lines are a first connecting straight line and a second straight line formed by connecting each of the two reference positions adjacent to the nearest reference position and the nearest reference position. It may contain connecting lines.

In an embodiment of the present invention, a first vertical connection line connected from the actual position to the first connecting straight line and a first projection point that is an intersection of the first connecting straight line, and connected from the actual position to the second connecting straight line A second projection point that is the intersection of the second vertical connecting line and the second connecting straight line may be set.

In an embodiment of the present invention, the contour reference position and the contour reference direction may be determined according to positions of the first projection point and the second projection point with respect to the first connecting straight line and the second connecting straight line, respectively. there is.

In an embodiment of the present invention, when the first projection point is located on an extension of the first connecting straight line and the second projection point is located on an extension of the second connecting straight line, the closest reference position is the contour reference position can be set.

In an embodiment of the present invention, in the fourth step, the outline reference direction may be a reference direction at the nearest reference position.

In an embodiment of the present invention, when the first projected point is positioned on an extension of the first connecting straight line and the second projected point is positioned on the second connecting straight line, the second projected point is set as the contour reference position. It can be.

In an embodiment of the present invention, when the first projected point is located on the first connecting straight line and the second projected point is located on an extended line of the second connecting straight line, the first projected point is set as the contour reference position. It can be.

In an embodiment of the present invention, when the first projection point is located on the first connection straight line and the second projection point is located on the second connection straight line, the first projection point and the second projection point are A projected point closer to the actual position may be set as the contour reference position.

In an embodiment of the present invention, in the fourth step, the contour reference direction is a quaternion spherical linear shape using a reference direction at the nearest reference position and a reference direction at a reference position adjacent to the nearest reference position. It can be obtained by interpolation (SLERP) operation.

In an embodiment of the present invention, in the fourth step, the contour reference direction may be a vector direction of an axis formed along a longitudinal direction of the tool at the contour reference position.

In an embodiment of the present invention, in the first step, the actual position of the tool can be measured through transformation matrix multiplication in which a uniform transformation matrix (HTM) is multiplied by a matrix for the position of a reflector coupled to the processing unit. .

The configuration of the present invention for achieving the above object is coupled to the robot and processing unit having the tool; a laser tracker for measuring the actual position and direction, which are the real-time position and direction of the tool, by radiating a laser to the processing unit; The reference position and the reference direction, which are the position and direction of the tool, are set on the reference machining path, which is the machining path of the tool previously set according to the target to be processed, and information on the actual position and the actual direction is obtained from the laser tracker. and a controller that controls the position and direction of the tool by receiving the information, deriving the contour reference position and the contour reference direction, and transmitting a control signal to the robot.

In an embodiment of the present invention, the control unit may transmit a control signal to the robot so that the tool moves from the actual position to the contour reference position and changes its attitude from the actual direction to the contour reference direction.

The effect of the present invention according to the configuration as described above is that the performance of error correction can be improved because the error correction of the machining path for the machining target is performed using the difference between the actual position of the tool and the reference position set in advance. .

And, the effect of the present invention is that it is possible to perform error correction control for the robot while minimizing an additional separate device or complicated calculation, so that the efficiency in the machining process using the robot can be significantly improved.

The effects of the present invention are not limited to the above effects, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a schematic diagram of position correction of a tool according to an embodiment of the present invention.
2 is a graph of position correction of a tool according to an embodiment of the present invention.
Figure 3 is a schematic diagram of a robot control device according to an embodiment of the present invention.
4 is an image for explanation of each case for measuring the contour reference position according to an embodiment of the present invention.
5 is an image of measurement of directional contour error according to an embodiment of the present invention.
6 is a design diagram of a processing target according to an embodiment of the present invention.
7 is an image of robot processing using a robot control device according to an embodiment of the present invention.

Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms, and therefore is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, when a part is said to be "connected (connected, contacted, combined)" with another part, this is not only "directly connected", but also "indirectly connected" with another member in between. "Including cases where In addition, when a part "includes" a certain component, it means that it may further include other components without excluding other components unless otherwise stated.

Terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "include" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram of position correction of a tool 111 according to an embodiment of the present invention, and FIG. 2 is a graph of position correction of a tool 111 according to an embodiment of the present invention. And, Figure 3 is a schematic diagram of a robot 120 control device according to an embodiment of the present invention.

During machining, the actual posture (actual position and orientation) of the tool 111 may deviate from the desired trajectory due to deflection mainly due to cutting forces, i.e., compliance errors and inaccuracies in kinematic parameters, resulting in contour errors. In the three-dimensional (3-D) robot 120 machining, the contour error is the positional contour error ε _p , which is the difference between the reference position and the actual position P _act of the tool 111, and the reference position of the tool 111 It can be composed of the direction contour error (ε _o ), which is the difference between the direction and the actual direction (O _act ).

As shown in FIGS. 1 and 2, using the reference pose and the actual pose, the contour reference pose including the contour reference position Pc and the contour reference direction Oc ) can be derived, and the posture error (ε contour) can be derived by the positional contour error (ε _p ) and the directional _contour error (ε _o ) in the robot 120 processing.

The position contour error (ε _p ) can be defined as the orthogonal distance from the actual position (P _act ) to the desired reference locus of Cartesian coordinates, and the position contour error (ε _p ) is the actual position (P _act ) and the actual position (P It can be calculated using the closest reference position (P _n ), which is the closest reference position in the reference trajectory in _act ). Further, the directional contour error ε _o can be calculated using the desired direction (the direction of the contour reference posture) and the actual direction. These matters will be described in detail in each of the remaining steps below.

Hereinafter, a method for controlling the robot 120 according to the present invention will be described.

First, in the first step, the laser tracker 200 is coupled to the robot 120 and irradiates a laser to the processing unit 110 having the tool 111 to determine the real-time position and direction of the tool 111 (actual position) P _act ) and actual direction (O _act ) can be measured. Here, the robot 120 may be a robot 120 having a plurality of links and joints, and the tool 111 may be a tool 111 that performs drilling, milling, polishing, and the like. However, it is not limited thereto.

As shown in FIG. 3, in order to accurately correct the position contour error (ε _p ) and the directional contour error (ε _o ) of the tool 111, the laser tracker 200 is used to correct the actual posture (position and position) of the tool 111. direction) can be measured. Here, the tool 111-related position may mean a 3-dimensional position of the end of the tool 111, and the tool 111-related direction may mean a z-axis vector direction extending in the longitudinal direction of the tool 111. Below, the same.

The actual position (P _act ) of the tool 111 may be measured through transformation matrix multiplication in which a uniform transformation matrix (HTM) is multiplied by a matrix for the position of the reflector 112 coupled to the processing unit 110 .

Specifically, in FIG. 3, {a}, {l}, {r}, and {t} denote the robot 120, the laser tracker 200, the 6-DOF reflector 112, and the tool 111, respectively. can represent the frame of Here, since it is not easy to directly measure the actual pose of the tool, it can be obtained indirectly using transformation matrix multiplication.

Specifically, the posture of the tool 111 with respect to the frame {a} of the robot 120 may be calculated as in [Equation 1] below.

[Equation 1]

은 균일변환행렬(HTM)이고 R, P 및 0은 각각 3x3 회전 행렬, 위치 벡터 및 1x3 제로 행렬을 나타낼 수 있다. 균일변환행렬(HTM)은, 프레임 {a}에서 프레임 {b}로의 변환 행렬, 또는, 프레임 {a}에 대한 프레임 {b}의 자세(또는 좌표)로 설명할 수 있다.

is a uniform transformation matrix (HTM), and R, P, and 0 may represent a 3x3 rotation matrix, a position vector, and a 1x3 zero matrix, respectively. A uniform transformation matrix (HTM) can be described as a transformation matrix from frame {a} to frame {b}, or a posture (or coordinates) of frame {b} with respect to frame {a}.

Here, T _at may be the posture of the tool 111 with respect to the frame ({a}) of the robot 120, and T _al is the laser tracker 200 ({l} in the frame ({a}) of the robot 120. ) may be a transformation matrix to And, T _lr may be the posture of the reflector 112 ({r}) with respect to the laser tracker 200 ({l}), and T _rt is the frame of the tool 111 in the reflector 112 ({r}). It can be a transformation matrix to ({t}).

T _al and T _rt are constant matrices that are not affected by the machining process, but T _lr provided by the laser tracker 200 may change during machining as the link (manipulator) of the robot 120 moves.

In the second step after the first step as described above, the reference machining path, which is the machining path of the tool 111 set in advance according to the machining target 10, is divided into a plurality of straight lines, and the You can set the reference position and reference direction, which are positions and directions. Here, a plurality of straight lines may be formed by dividing a reference machining path by an interpolator.

The control unit 130 that controls the robot 120 may provide a set of reference postures composed of a reference position and a reference direction in each sampling period as shown in [Equation 2] below to plan a machining path of the robot 120. there is.

[Equation 2]

Here, Pr and Or may be the reference position and direction of Cartesian coordinates. In addition, Xr, Yr, and Zr may be reference positions of the X, Y, and Z axes, respectively. Further, Rx _r , Ry _r , and Rz _r may be reference directions of the Rx, Ry, and Rz axes, each represented by an Euler angle.

In order to derive the positional contour error (ε _p ) and the directional contour error (ε _o ), the reference posture as described above must be found, and the reference trajectory by the reference machining path is divided into a plurality of straight lines divided by an interpolator. As a result, A reference location may be created for each sampling period. Also, a reference direction, which is the direction of the tool 111 at each reference position, can be created.

In the third step after the second step as described above, each of the two straight lines passing through the nearest reference position (P _n ), which is the reference position closest to the actual position (P _act ) among the plurality of straight lines, and the actual position (P _act ) The contour reference position Pc, which is a position where the positional error of the tool 111 is corrected, can be derived using two vertical connecting lines vertically connecting . Here, the two straight lines may include a first connecting straight line and a second connecting straight line formed by connecting each of the two reference positions adjacent to the nearest reference position (P _n ) and the nearest reference position (P _n ). .

The position contour error (ε _p ) can be calculated using the distance between the contour reference position (Pc) found on the line segment connecting the actual position (P _act ) and the interpolated reference position. To this end, first, a search range is set, a plurality of reference positions are set in the reference machining path within the search range, and then, among the plurality of reference positions, the closest reference position (P _act ) closest to the actual position of the tool 111 ( It can be derived by calculating P _n ).

Here, the plurality of reference positions within the search range may be preferably 20 or more experimentally, but are not necessarily limited thereto.

After deriving the nearest reference position (P _n ) as described above, two reference positions adjacent to the nearest reference position (P _n ), that is, the closest reference position (P _n ) with respect to the machining direction on the reference machining path A first adjacent reference position (P _n−1 ) and a second adjacent reference position (P _n+1 ), which are two reference positions located in the forward and backward directions, may be set.

Here, a first connecting line is formed by connecting the first adjacent reference position (P _n−1 ) and the nearest reference position (P _n ), and the second adjacent reference position (P _n+1 ) and the nearest reference position ( A second connection straight line may be formed by connecting P _n ).

And, the first vertical connecting line connected to the first connecting straight line from the actual position (P _act ) and the first projection point (H ₁ ) which is the intersection of the first connecting straight line, and the second connecting straight line from the actual position (P _act ) A second projection point (H ₂ ), which is an intersection of the connected second vertical connecting line and the second connecting straight line, may be set.

The contour reference position (Pc) can be derived according to each case using the closest reference position (P _n ) and the first projection point (H ₁ ) and the second projection point (H ₁ ) as described above. It will be explained in detail below.

4 is an image for explanation of each case for measuring the contour reference position Pc according to an embodiment of the present invention. Figure 4 (a) is for the first case, Figure 4 (b) is for the second case, Figure 4 (c) is for the third case. And, (d) of FIG. 4 is for the fourth case.

As shown in FIG. 4, the contour reference position Pc and the contour reference direction Oc may be determined according to the positions of the first projection point and the second projection point with respect to the first connecting straight line and the second connecting straight line, respectively. . Specifically, four cases may be established, and the actual position (based on the position of each of the first projection point (H ₁ ) and the second projection point (H ₁ ) for each of the first connecting straight line and the second connecting straight line ( A contour reference position Pc for P _act ) may be determined.

And, as shown in [Equation 3-1] and [Equation 3-2] below, the calculation of the first projection point (H ₁ ), the second projection point (H ₁ ), and the contour reference position (Pc) r1 and r2 can be defined to determine the weights for

[Equation 3-1]

=

=

[Equation 3-2]

=

=

Here, Pc may indicate a contour reference position, P _n−1 may indicate a first neighboring reference position, and P _n+1 may indicate a second neighboring reference position. Also, H ₁ may represent a first projection point, and H ₂ may represent a second projection point.

As shown in (a) of FIG. 4, as a first case, the first projection point (H ₁ ) is located on the extension of the first connecting straight line and the second projection point (H ₂ ) is on the extension of the second connecting straight line. When located at , the closest reference position P _n may be the contour reference position Pc.

In case of the first case, since r ₁ >1 and r ₂ >1, the closest reference position P _n to the actual position P _act may be the contour reference position Pc.

As shown in (b) of FIG. 4, as a second case, the first projection point (H ₁ ) is located on the extension of the first connecting straight line and the second projecting point (H ₂ ) is located on the second connecting straight line. In this case, the second projection point H ₂ may be the contour reference position Pc.

And, as shown in (c) of FIG. 4, as a third case, the first projection point (H ₁ ) is located on the first connecting straight line and the second projecting point (H ₂ ) is on the extension line of the second connecting straight line. When located at , the first projection point H ₁ may be the contour reference position Pc.

In the case of the second case and the third case, one projection point of the first projection point (H ₁ ) and the second projection point (H ₂ ) is located inside one connecting straight line, and the other projected point is located on the other connecting straight line. may be located outside. Also, r ₁ and r ₂ , and a projected point positioned inside the connecting straight line, that is, on the connecting straight line may be the contour reference position Pc.

As shown in (d) of FIG. 4, as a fourth case, when the first projection point (H ₁ ) is located on the first connecting straight line and the second projected point (H ₂ ) is located on the second connecting straight line. , a projection point closer to the actual position P _act among the first projection point H ₁ and the second projection point H ₂ may be the contour reference position Pc.

In the case of the fourth case, the first projection point (H ₁ ) and the second projection point (H ₂ ) are located inside the first connecting straight line and the second connecting straight line, respectively, and 0≤r ₁ ≤1 and 0≤r ₂ ≤ 1, and the projected point closest to the actual position (P _act ) may be the contour reference position (Pc).

And, in the second to fourth cases as described above, the contour reference position Pc on the connecting line is the nearest reference by [Equation 4-1] or [Equation 4-2] below. It can be calculated using linear interpolation of the first neighboring reference position (P _n-1 ) and the second neighboring reference position (P _n+1 ), which are reference positions adjacent to the _position (P n ).

[Equation 4-1]

[Equation 4-2]

Here, Pc may indicate a contour reference position, P _n−1 may indicate a first neighboring reference position, and P _n+1 may indicate a second neighboring reference position.

And, the position contour error (ε _p ) can be calculated between the reference position and the actual position (P _act ) as shown in [Equation 5] below.

[Equation 5]

Here, ε _p denotes a positional contour error, Pc denotes a contour reference position, and Pa denotes an actual position (P _act ).

In the fourth step after the third step as described above, the reference direction at the nearest reference position (P _n ) and the actual direction (O _act ) are used to correct the direction error of the tool 111, and the contour reference direction ( Oc) can be derived.

Since general control of the robot 120 is intuitive, Euler angles can be used to express the direction of the tool 111 . However, Euler angles may not be suitable for handling orientation corrections because a change in one axis will affect the other axis due to sequential rotation.

Therefore, since quaternion (quaternion) simultaneously processes the rotation axis and is more efficient than rotation matrix, it can be easy to calculate direction. The directional contour error (ε _o ) can be calculated using the reference direction and the actual direction (O _act ), and the contour reference direction (Oc) is determined in a different way according to each case in the above-described third step. can be derived.

Specifically, in the case of the first case described above, the outline reference direction Oc may be a reference direction at the nearest reference position P _n . In the case of the second to fourth cases described above, the contour reference direction Oc is a reference direction at the nearest reference position P _n and a reference position adjacent to the nearest reference position P _n (first It can be obtained by a quaternion spherical linear interpolation (SLERP) operation using reference directions at the adjacent reference position (P _n−1 ) and the second adjacent reference position (P _n+1 ).

In the second to fourth cases, the outline reference direction Oc is the nearest reference direction O _n , which is a reference direction at the nearest reference position P _n , and the first neighboring reference position P _{n - 1} ) and the second neighboring reference position (P _{n + 1} ) quaternion of the first neighboring reference direction (O _n-1 ) and the second neighboring reference direction (O n + 1 ) respectively (P _{n + 1} ) spherical linear shape It can be obtained by interpolation (SLERP) operation. Here, the quaternion spherical linear interpolation (SLERP) operation can be performed by [Equation 6-1] and [Equation 6-2] below.

[Equation 6-1]

[Equation 6-2]

Here, as described above, q _c denotes the quaternion of the contour reference direction (Oc), q _n denotes the quaternion of the nearest reference direction (O _n ), and q _n-1 is the first neighboring reference direction (O _{n -1} ) can represent the quaternion. Also, q _n+1 may represent a quaternion of the second adjacent reference direction (O _n+1 ).

In addition, the 3D coordinates for the directional contour error ε _o can be derived using the difference between the 3D coordinates of the contour reference direction Oc obtained as described above and the 3D coordinates of the actual direction O _act . . This will be described in detail in the description of the fifth step below.

In addition to one method of deriving the contour reference direction Oc as described above, the contour reference direction Oc may be a vector direction of an axis formed along the longitudinal direction of the tool 111 at the contour reference position Pc. Here, the axis vector formed along the longitudinal direction of the tool 111 may be the z-axis vector of the tool 111 .

Specifically, in order to calculate the directional contour error ε _o , the z-axis vector may be extracted from the actual direction O _act at the actual position P _act and the reference direction at the contour reference position Pc. And, as shown in [Equation 7] below, the directional contour error (ε _o ) is calculated using the angle difference between the actual direction (O _act ) and the z-axis vector of each reference direction in the contour reference position (Pc). It can be.

[Equation 7]

Here, ε _o denotes a directional contour error, ν' _c denotes a z-axis vector of a reference direction in the contour reference position Pc, and ν _a may denote a z-axis vector of an actual direction O _act .

In addition, the contour reference direction Oc can be derived by correcting the angular difference using the directional contour error ε _o as described above.

In the fifth step after the fourth step as described above, the position and direction of the tool 111 can be controlled by controlling the robot 120 using the contour reference position Pc and the contour reference direction Oc. As described above, for the tool 111, the position contour error ε p can be derived using the actual position P _act and the contour reference position Pc, _{and the actual direction O act and} the contour reference direction Orientation contour error (ε _o ) can be derived using (Oc). In addition, a control signal may be transmitted to the robot 120 to change the position and direction of the tool 111 so that the positional contour error ε _p and the directional contour error ε _o are corrected.

The control signal as described above is generated by the control unit 130 described below, the joint axes of the robot 120 are individually controlled, and the controllers for each of the individual axes are composed of a cascade control structure connected to position, velocity, and current loops. can In such a controller 130, the positional contour error ε _p and the directional contour error ε _o can be derived using the contour control algorithm as described above.

Since the prior art robot 120 controller does not allow modification of the internal control structure, an additional PI (proportional-integral) position control loop is designed in Cartesian coordinates to correct the contour error, so that the control unit of the present invention ( 130) can be formed.

Accordingly, the following [Equation 8] may be derived by modifying [Equation 2] described above.

[Equation 8]

Here, P _r,m may be a modified reference position, and O _r,m may be a modified reference direction. Also, K _PI may be a PI control gain for each axis, and may represent a positional contour error (ε _p ) and a directional contour error (ε _o ) for each axis.

Accordingly, the position correction amount of the tool 111 may be expressed as in [Equation 9] below.

[Equation 9]

Here, is the position contour error (ε _p ) for each axis, Pc is the contour reference position, and Pa is the actual position (P _act ).

In order to compensate for the directional contour error (ε _o ), the z-axis vector can be used as described above. In this case, as shown in [Equation 10], the actual direction (O _act ) and the contour reference position (Pc) ), a unit direction vector (n) orthogonal to each z-axis vector of the reference direction may be generated. Then, error correction for the unit direction vector n may be performed by the amount of the directional contour error ε _o .

[Equation 10]

Here, n is a unit direction vector, ν _a represents the z-axis vector of the actual direction (O _act ), and ν _c represents the z-axis vector of the reference direction in the contour reference position Pc.

5 is an image of measurement of a directional contour error (ε _o ) according to an embodiment of the present invention.

To compensate for the directional contour error (ε _o ), quaternion spherical linear interpolation (SLERP) can be used as described above, and the quaternion is calculated using a unit direction vector (n) and rotation amount (ε _o ), and Euler can be converted to an angle. By the following [Equation 11], q -> E may represent a conversion from a quaternion to an Euler angle.

[Equation 11]

Here, n is the unit direction vector, and is the directional contour error (ε _o ) for each axis.

Hereinafter, the robot 120 control device of the present invention will be described.

The robot 120 control apparatus of the present invention for performing the robot 120 control method of the present invention is coupled to the robot 120 and includes a processing unit 110 having a tool 111; Laser tracker 200 for measuring the real-time position and direction of the tool 111 by irradiating a laser to the processing unit 110 (P _act ) and the actual direction (O _act ); The reference position and reference direction, which is the position and direction of the tool 111 on the reference machining path, which is the machining path of the tool 111 set in advance according to the processing target 10, are set, and the actual position (P) from the laser tracker 200 _act ) and the actual direction (O _act ) are received, the contour reference position (Pc) and the contour reference direction (Oc) are derived, and a control signal is transmitted to the robot 120, thereby determining the position of the tool 111 and the position of the tool 111. A control unit 130 for controlling the direction; includes. Here, the controller 130 controls the robot 120 so that the tool 111 moves from the actual position P _act to the contour reference position Pc and changes its posture from the actual direction O _act to the contour reference direction Oc. ) to transmit the control signal.

The first step described above may be performed by the laser tracker 200, and each control-related matter performed in the second to fifth steps described above may be performed by the control unit 130.

The remaining details of the robot 120 control device of the present invention are the same as those described in relation to the method of controlling the robot 120 of the present invention.

The robot 120 control device of the present invention formed as described above; and a display device displaying numerical values for correction amounts in the shape of the robot 120, the reference machining path, and the contour reference position Pc and the contour reference direction Oc for the tool 111, respectively. can do.

The display device may display some or all of the three-dimensional shape of the robot 120 and each of the numerical values described above, and the user may observe the operating conditions of the robot 120 and the tool 111 while viewing the display screen. can be checked with

6 is a design diagram of a processing target 10 according to an embodiment of the present invention, and FIG. 7 is an image of robot 120 processing using a robot 120 control device according to an embodiment of the present invention.

6 is a design diagram for a processing target 10 for testing the performance of the robot 120 control method of the present invention using the robot 120 control device of the present invention and is stored in the control unit 130, in FIG. 6 ( a) is a plan view of the target 10, FIG. 6(b) is a side view of the target 10, and FIG. 6(c) is a perspective view of the target 10.

In order to measure the improvement in processing precision by the robot 120 control method of the present invention as described above, the robot 120 (TX200, Staubli), the spindle (ES929A, HSD) and the laser tracker 200 system (AT960MR, Leica geosystems ) A robot 120 control device composed of was provided.

A spindle is attached to the processing unit 110, which is an end effector of the robot 120, and a 6-DOF sensor (T-Mac, Leica geosystems) is attached to the processing unit 110 as a reflector 112. The laser tracker 200 can measure the position and direction of the reflector 112 in real time up to 1 kHz, and the algorithm by the robot 120 control method of the present invention as described above is executed on an industrial PC (C6930, Beckhoff). It was implemented in the Beckhoff TwinCAT real-time programming environment and ran at a sample rate of 250 Hz. The real-time PC can collect space measurement data from the laser tracker 200 controller and exchange tool 111 path and correction values with the robot 120 controller (CS8C, Stδubli) using the EtherCAT protocol.

In order to compare and evaluate the performance of the algorithm by the control method of the robot 120 of the present invention, since the NAS 979 workpiece is widely recognized as a performance test for a 5-axis machine tool, as shown in FIG. 6, the robot as described above ( 120) A National Aerospace Standard (NAS) 979 work piece was machined using a control device.

At this time, the performance was evaluated by processing circles, squares, and side slopes. The machining conditions were determined as feed speed 900 mm/min, spindle speed 6,000 rpm, and depth of cut 2 mm (refer to ISO 10791-1).

The dimensional accuracy of the workpiece, which is the processed processing target 10, was measured using a coordinate measuring machine (CMM). The repeatability of the coordinate measuring machine (CMM) is 0.006 mm and the volume accuracy is 2.4 μm + length/250 mm. The diameter of the circle and the length of the square were measured, and the boundary of the circle was measured at 20 points and each side of the square was measured at 10 points.

Two workpieces as described above are provided, and one workpiece, a workpiece for implementation, was processed by applying the robot 120 control method of the present invention, and the other workpiece, a workpiece for comparison, applied the robot 120 control method of the prior art. It was processed.

Here, the target diameter of the circle is 108 mm, and the target length of each side of the square is 110 mm.

When the workpieces for comparison were measured after completion of machining for each workpiece, the diameter of the measured circle was 108.322mm, the machining error of the circle was 322㎛, and the measured lengths of the square were 110.356 and 110.353mm for each side, respectively. The processing error of the square was 356 μm.

On the other hand, when the workpiece for practice was measured, the diameter of the measured circle was 107.945mm, and the machining error of the circle was 55㎛, and the measured lengths of the square were 110.049 and 109.950mm for each side, so the machining error of the square was 50 μm.

As can be seen from the comparison of machining errors after machining of the workpiece for comparison and the workpiece for implementation described above, it can be confirmed that machining accuracy is improved when machining the workpiece using the robot 120 control method of the present invention.

In the case of using the robot 120 control method and device of the present invention as described above, using the difference between the actual position (P _act ) of the tool 111 and the reference position set in advance, the machining path for the machining target 10 Since error correction is performed, performance of error correction can be improved.

In addition, it is possible to perform error correction control for the robot 120 while minimizing an additional separate device or complicated calculation, so that efficiency in a machining process using the robot 120 can be significantly improved.

The above description of the present invention is for illustrative purposes, and those skilled in the art can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be interpreted as being included in the scope of the present invention.

10: processing target 110: processing unit
111: tool 112: reflector
120: robot 130: control unit
200: laser tracker

Claims (16)

A first step in which a laser tracker is coupled to a robot and irradiates a laser to a processing unit having a tool to measure the real position and direction of the tool in real time;
A second step of dividing a reference machining path, which is a machining path of the tool previously set according to a machining target, into a plurality of straight lines, and setting a reference position and direction, which are the position and direction of the tool, on the reference machining path;
The position where the position error of the tool is corrected using two straight lines each passing through the nearest reference position, which is the reference position closest to the actual position among the plurality of straight lines, and two vertical connecting lines vertically connecting the actual position. a third step of deriving the reference position of the contour;
a fourth step of deriving a contour reference direction, which is a direction obtained by correcting a direction error of the tool, using the reference direction and the actual direction at the nearest reference position; and
and a fifth step of controlling the position and direction of the tool by controlling the robot using the contour reference position and the contour reference direction.
The method of claim 1,
In the second step, the plurality of straight lines is a robot control method using laser tracker feedback, characterized in that formed by dividing the reference machining path by an interpolator.
The method of claim 1,
In the third step, the two straight lines include a first connecting straight line and a second connecting straight line formed by connecting each of the two reference positions adjacent to the nearest reference position and the nearest reference position. Robot control method using laser tracker feedback.
The method of claim 3,
A first vertical connection line connected from the actual position to the first connection straight line and a first projection point that is an intersection of the first connection straight line, and a second vertical connection line connected from the actual position to the second connection straight line and the first projection point. A robot control method using laser tracker feedback, characterized in that the second projection point, which is the intersection of two connecting lines, is set.
The method of claim 4,
The laser tracker feedback, characterized in that the contour reference position and the contour reference direction are determined according to the position of each of the first projection point and the second projection point with respect to each of the first connecting line and the second connecting straight line. Robot control method used.
The method of claim 5,
When the first projection point is located on the extension of the first connecting line and the second projection point is located on the extension of the second connecting straight line, the nearest reference position is set as the contour reference position. Robot control method using laser tracker feedback.
The method of claim 6,
In the fourth step, the robot control method using laser tracker feedback, characterized in that the contour reference direction is the reference direction at the nearest reference position.
The method of claim 5,
When the first projected point is located on an extension of the first connecting line and the second projected point is located on the second connecting straight line, the second projected point is set as the contour reference position. Robot control method using.
The method of claim 5,
When the first projected point is located on the first connecting straight line and the second projected point is located on an extension of the second connecting straight line, the first projected point is set as the contour reference position. Robot control method using.
The method of claim 5,
When the first projection point is located on the first connection line and the second projection point is located on the second connection line, the projection point closest to the actual position among the first projection point and the second projection point is the Robot control method using laser tracker feedback, characterized in that set to the contour reference position.
According to claims 8 to 10,
In the fourth step, the contour reference direction is obtained by a quaternion spherical linear interpolation (SLERP) operation using a reference direction at the nearest reference position and a reference direction at a reference position adjacent to the nearest reference position. Robot control method using laser tracker feedback, characterized in that.
According to claims 7 to 10,
In the fourth step, the robot control method using laser tracker feedback, characterized in that the contour reference direction is a vector direction of an axis formed along the longitudinal direction of the tool at the contour reference position.
The method of claim 1,
In the first step, the robot using laser tracker feedback, characterized in that the actual position of the tool is measured through transformation matrix multiplication that multiplies the matrix for the position of the reflector coupled to the processing unit by a uniform transformation matrix (HTM) control method.
In the robot control device using laser tracker feedback for performing the robot control method using laser tracker feedback of claim 1,
a processing unit coupled to the robot and having the tool;
a laser tracker for measuring the actual position and direction, which are the real-time position and direction of the tool, by radiating a laser to the processing unit;
The reference position and the reference direction, which are the position and direction of the tool, are set on the reference machining path, which is the machining path of the tool previously set according to the target to be processed, and information on the actual position and the actual direction is obtained from the laser tracker. and a control unit for controlling the position and direction of the tool by receiving the information, deriving the contour reference position and the contour reference direction, and transmitting a control signal to the robot. .
The method of claim 14,
The controller controls the robot using laser tracker feedback, characterized in that the controller transmits a control signal to the robot so that the tool moves from the actual position to the contour reference position and changes its posture from the actual direction to the contour reference direction. Device.
A robot control device using laser tracker feedback according to claim 14; and
and a display device displaying numerical values for correction amounts in the contour reference position and the contour reference direction, respectively, for the shape of the robot, the reference machining path, and the tool.

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