CN113305474A - Welding robot welding attitude interpolation method based on PLC - Google Patents

Abstract

The invention proposes a PLC-based welding robot swing welding attitude interpolation method, including: teaching the starting point P _s and the ending point P _e of the swing welding path to obtain position and attitude information; Compute the quaternion intermediate transformation Z _se of the starting point and the end point; Calculate the normalization constant N _const of the intermediate attitude transformation Z _se ; Calculate the transformation angle φ of the intermediate quaternion transformation Z _se of the attitude; Calculate the intermediate attitude interpolation point _{P i from} the welding path P _s to Pe; generate the attitude interpolation point, and judge whether it is the end point; combine the spatial position interpolation information and attitude interpolation information from the starting point to the ending point of the welding path, the welding robot PLC The controller converts the interpolation information into the corresponding joint angle information through the inverse solution module, and sends it to the robot actuator for execution through bus communication.

Description

A PLC-based Welding Welding Attitude Interpolation Method of Welding Robot

technical field

The invention relates to the technical field of welding robot control, in particular to a PLC-based welding robot swing welding attitude interpolation method.

Background technique

In practical engineering applications, welding robots are often used for straight line and arc trajectory welding, but when the weld is relatively large or in order to meet special welding process requirements, swing welding (referred to as swing welding) is often used. Weaving welding refers to a method in which the electrode at the end of the robot travels along the direction of the welding seam, and at the same time oscillates with a set amplitude and frequency to increase the welding width, thereby improving the welding efficiency and strength. Commonly used swing welding includes triangular swing welding, L-shaped swing welding, sinusoidal swing welding, etc. It effectively improves the strength and toughness of the weld and is widely used in automated welding equipment.

The trajectory planning of swing welding is based on the upper layer of robot motion planning. According to the welding path taught by the user, a straight line or other curve is used to fit the welding path of the welding seam. In some special applications, in order to meet the process requirements or avoid the collision between the welding robot and the tooling, it is necessary to change the attitude of the robot end during the welding process; especially when performing arc weaving welding, it is necessary to teach the arc weaving welding. the intermediate position and attitude to avoid tool interference.

Existing welding robot swing welding technology mostly studies the swing welding method from the perspective of plane position and spatial position, and uses different curves to fit the welding path. Attitude planning, the robot is easy to collide with the tooling during the swing welding process. At the same time, the robot posture changes suddenly at the welding end point, which affects the welding effect. Chinese patent CN105855672B provides a space arc interpolation welding method based on a teaching robot. The pose is based on rotation matrix interpolation, and the teaching point in the robot coordinate system needs to be converted to the plane where the arc is located, and the calculation process is complicated.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve at least one of the technical defects.

Therefore, the purpose of the present invention is to propose a PLC-based welding robot swing welding attitude interpolation method.

In order to achieve the above object, an embodiment of the present invention provides a PLC-based method for interpolating a weaving welding posture of a welding robot, including the following steps:

Step S1, teaching the starting point P _s and the ending point _Pe of the swing welding path to obtain position and attitude information;

Step S2, converting the welding path point attitude description into a quaternion representation;

Step S3, calculate the quaternion attitude intermediate transformation Z _se of the starting point and the ending point;

Step S4, calculating the normalization constant N _const of the intermediate attitude transformation Z _se ;

Step S5, calculate the transformation angle φ of the quaternion transformation Z _se in the middle of the attitude;

，再计算插补点P_i的姿态信息；Step S6, calculate the attitude information of the ith interpolation point P _i from the welding path P _s to P _e ; then first calculate the attitude insertion angle of the interpolation point P _i

, and then calculate the attitude information of the interpolation point _Pi ;

Step S7, generate an attitude interpolation point, determine whether it is the end point, if so, the interpolation ends, otherwise return to step S6;

Step S8, combining the spatial position interpolation information from the starting point to the end point of the welding path and the attitude interpolation information in step S7, the welding robot PLC controller converts the interpolation information into the corresponding joint angle information through the inverse solution calculation module, and passes The method of bus communication is sent to the robot actuator for execution.

Further, in the step S1, the starting point P _s and the ending point P _e of the welding path are taught, and the position and attitude information P (x, y, z, α, β, γ) based on the robot coordinate system are obtained. ; The robot pose information is jointly described by the position vector (x, y, z) based on the rectangular space and the pose vector (α, β, γ) based on the Euler space.

Further, in the step S2,

欧拉角转换成四元数公式下所示：Convert the attitude vectors of the starting points P _s and _Pe of the welding path to the quaternion space, then the attitude Z = [Z _w Z _x Z _y Z _z ] ^T can be described by the unit quaternion, and

The Euler angles are converted to quaternion formulas as follows:

Further, in step S3, the intermediate transformation from the starting point P _s to the ending point _Pe of the welding path is calculated, including:

Assuming that the attitude quaternions of the points P _s and Pe are Z _s and Z _e in turn _, and the intermediate transformation of the quaternions is Z _se , then:

From the properties of the identity matrix, it can be known that the inverse Z ^of the identity matrix is equal to its conjugate Z ^* , then the above formula can be further converted into the following formula:

further,

Z_e为：

_Ze is:

代入式(3)即可得四元数中间变换Z_se：Then the above _Ze and

Substitute into equation (3) to get the quaternion intermediate transformation Z _se :

Further, the calculation of the normalization constant N _const of the intermediate transformation of the attitude includes the following steps:

所求得中间变换的四元数Z_se为

则四元数的归一化常数N_const可由下式表式：Suppose by

The obtained intermediate transformation quaternion Z _se is

Then the normalization constant N _const of the quaternion can be expressed by the following formula:

Further, in the step S4, calculating the intermediate transformation Z _se transformation angle φ includes the following steps:

旋转某一角度φ，由四元数与三维旋转之前关系可得四元数变换角：The rotation transformation of robot attitude can be described either by quaternions or by the axis-angle relationship, that is, the attitude transformation represented by quaternions is expressed as a rotation axis defined by a unit vector

Rotate a certain angle φ, and the quaternion transformation angle can be obtained from the relationship between the quaternion and the three-dimensional rotation:

Further, the calculation of the intermediate interpolation point P _i of the attitude change from the welding path P _s to the P _e includes the following steps:

The attitude interpolation of the welding path starting point P _s to the ending point _Pe can be converted into an interpolation of the rotation angle φ of the intermediate transformation Z _se . Assuming that the number of swing interpolation of the welding path position is N, and the intermediate interpolation point i of the attitude is 1, 2, ..., (N-1); the information of the intermediate interpolation point P _i of the attitude is calculated as follows:

则四元数姿态变换的第一个元素为：a) Suppose the attitude change angle of the ith interpolation point relative to the welding starting point is

Then the first element of the quaternion pose transformation is:

b) Combined with the normalization constant of the intermediate transformation Z _se , the intermediate calculation variable κ can be obtained:

c) The attitude change quaternion Z _si of the intermediate attitude transformation interpolation point relative to the arc starting point can be expressed by the following formula:

Then the attitude quaternion Z _i of the interpolation point is:

Z _i =Z _si ·Z _s

P_i的欧拉角为(α_i,β_i,γ_i)，则：d) Convert the attitude quaternion Z _i of the interpolation point P _i into Euler angles (RPY), assuming

The Euler angles of P _i are (α _i ,β _i ,γ _i ), then:

e) Repeat steps a to d until all intermediate interpolation points are calculated; the last interpolation point is the end point P _e of the swing welding

According to the PLC-based welding robot weaving welding attitude interpolation method, developed based on the PLC welding robot controller, during the swing trajectory planning, the posture of the welding path point is planned, which effectively avoids the robot swing welding process. Tooling collision problem. At the same time, the present invention performs planning and interpolation on the posture of the welding robot in the quaternion space, so as to ensure the smoothness of the posture of the robot and improve the welding quality.

1. During the swing trajectory planning of the present invention, the posture is planned and interpolated, which effectively avoids the collision problem with the tooling during the robot swing welding process;

2. The present invention performs planning and interpolation on the posture in the quaternion space, and does not involve coordinate transformation, and the algorithm is simple and efficient;

3. The present invention is based on the attitude interpolation method of quaternion, the attitude change of the welding robot is smooth and stable during the swing welding process, and the welding quality is improved.

Additional aspects and advantages of the present invention will be set forth, in part, from the following description, and in part will be apparent from the following description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings, wherein:

1 is a flowchart of a PLC-based welding robot weaving welding posture interpolation method according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a PLC-based welding robot weaving welding posture interpolation method according to an embodiment of the present invention.

Detailed ways

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, and are intended to explain the present invention and should not be construed as limiting the present invention.

As shown in FIG. 1 and FIG. 2 , the PLC-based welding robot weaving welding posture interpolation method according to the embodiment of the present invention includes the following steps:

In step S1, the starting point P _s and the ending point _Pe of the swing welding path are taught to obtain the position and attitude information.

In this step, the starting point P _s and the ending point P _e of the welding path are taught, and the position and attitude information P (x, y, z, α, β, γ) based on the robot coordinate system is obtained; the robot pose The information is jointly described by the position vector (x, y, z) based on the rectangular space and the pose vector (α, β, γ) based on the Euler space.

Specifically, through the welding robot teach pendant, teach the starting point P _s and the ending point P _e of the swing welding path, and obtain the position and attitude information P _s (x _s , y _s , z _s , based on the robot coordinate system) α _s , β _s , γ _s ) and P _e (x _e , y _e , _ze , α _e , β _e , γ _e ).

In step S2, the gesture description of the welding path point is converted into a quaternion representation.

欧拉角转换成四元数公式下所示：In the embodiment of the present invention, the attitude vectors of the starting points P _s and P _e of the welding path are converted into the quaternion space, then the attitude of the points can be described by the unit quaternion Z = [Z _w Z _x Z _y Z _z ] ^T , and

The Euler angles are converted to quaternion formulas as follows:

The attitudes (α, β, γ) of the starting point P _s and the end point _Pe of the swing welding are converted into quaternion description by formula (1), then the corresponding attitude quaternions of P _s and _Pe are as follows:

Step S3, calculate the quaternion pose intermediate transformation Z _se of the starting point and the ending point.

In this step, the intermediate transformation from the starting point P _s to the ending point _Pe of the welding path is calculated, including:

Assuming that the attitude quaternions of the points P _s and Pe are Z _s and Z _e in turn _, and the intermediate transformation of the quaternions is Z _se , then:

From the properties of the identity matrix, it can be known that the inverse Z ^of the identity matrix is equal to its conjugate Z ^* , then the above formula can be further converted into the following formula:

Z_e为：in,

_Ze is:

代入式(3)即可得四元数中间变换Z_se：Then the above _Ze and

Substitute into equation (3) to get the quaternion intermediate transformation Z _se :

Step S4, calculate the normalization constant N _const of the intermediate attitude transformation Z _se .

Specifically, calculating the normalization constant N _const of the intermediate attitude transformation includes the following steps:

则四元数的归一化常数N_const可由下式(4)表式：Assuming that the quaternion Z _se of the intermediate transformation obtained by formula (3) is

Then the normalization constant N _const of the quaternion can be expressed by the following formula (4):

Step S5, calculate the transformation angle φ of the intermediate quaternion transformation Z _se of the attitude.

Specifically, calculating the transformation angle φ of the intermediate transformation Z _se includes the following steps:

旋转某一角度φ，由四元数与三维旋转之前关系，结合所求Z_se可得四元数变换角：The rotation transformation of robot attitude can be described either by quaternions or by the axis-angle relationship, that is, the attitude transformation represented by quaternions is expressed as a rotation axis defined by a unit vector

Rotate a certain angle φ, according to the relationship between the quaternion and the three-dimensional rotation, combined with the required Z _se , the quaternion transformation angle can be obtained:

Step S6, calculating the attitude information of the _{ith interpolation point P i from} the welding path P _s to Pe.

Specifically, calculating the attitude information of the intermediate i-th interpolation point P _i from the attitude change from the welding path P _s to the P _e includes the following steps:

The attitude interpolation of the welding path starting point P _s to the ending point _Pe can be converted into an interpolation of the rotation angle φ of the intermediate transformation Z _se . Assuming that the number of swing interpolation of the welding path position is N, the total number of attitude interpolation cycles is N, and the intermediate interpolation point i of the attitude is 1, 2, . . . , (N-1). The information of the interpolation point P _i in the middle of the attitude is calculated as follows: First, the attitude interpolation angle of the interpolation point _Pi is calculated, and then the attitude information of the interpolation point _Pi is calculated.

a) The attitude change angle of the ith interpolation point relative to the welding starting point is:

其中，

插补点P_i的姿态插角

in,

_Attitude insertion angle of interpolation point Pi

Then the first element of the attitude transformation can be obtained as:

b) Combined with the normalization constant of the intermediate transformation Z _se , the intermediate calculation variable κ can be obtained:

c) Calculate the attitude change quaternion Z _si of the intermediate attitude transformation interpolation point relative to the arc starting point

Then the attitude quaternion Z _i of the interpolation point is:

Z _i = Z _si · Z _s (9)

Combining equations (6), (7), (8) and (9), the attitude quaternion of the interpolation point i of the swing welding can be obtained as:

d) Convert the attitude quaternion Z _i of the interpolation point P _i into Euler angles (α _i , β _i , γ _i ):

则P_i的欧拉角可由式(10)所得：Assumption

Then the Euler angles of P _i can be obtained from equation (10):

The Euler angle of the interpolation point P _i can be obtained by combining the Z _i obtained in the sub-step c) and the formula (10).

Among them, the attitude information of the interpolation point P _i is described by the Euler angle obtained by the above calculation, and is converted into a quaternion for description in the actual interpolation operation, and the interpolation is performed by the rotation angle transformed by the quaternion.

e) Repeat steps a to d until the poses of all the intermediate interpolation points are calculated; the last interpolation point is the end point P _e of the swing welding. In step S7, an attitude interpolation point is generated, and it is judged whether it is the end point. If so, the interpolation is ended, otherwise, it returns to step S6.

Step S8, combining the spatial position interpolation information from the starting point to the end point of the welding path and the attitude interpolation information in step S7, the welding robot PLC controller converts the interpolation information into the corresponding joint angle information through the inverse solution calculation module, and passes The method of bus communication is sent to the robot actuator for execution.

According to the PLC-based welding robot weaving welding attitude interpolation method, developed based on the PLC welding robot controller, during the swing trajectory planning, the posture of the welding path point is planned, which effectively avoids the robot swing welding process. Tooling collision problem. At the same time, the present invention performs planning and interpolation on the posture of the welding robot in the quaternion space, so as to ensure the smoothness of the posture of the robot and improve the welding quality.

1. During the swing trajectory planning of the present invention, the posture is planned and interpolated, which effectively avoids the collision problem with the tooling during the robot swing welding process;

2. The present invention performs planning and interpolation on the posture in the quaternion space, and does not involve coordinate transformation, and the algorithm is simple and efficient;

3. The present invention is based on the attitude interpolation method of quaternion, the attitude change of the welding robot is smooth and stable during the swing welding process, and the welding quality is improved.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and those of ordinary skill in the art will not depart from the principles and spirit of the present invention Variations, modifications, substitutions, and alterations to the above-described embodiments are possible within the scope of the present invention without departing from the scope of the present invention. The scope of the invention is defined by the appended claims and their equivalents.

Claims (8)

1. a PLC-based welding robot swing welding attitude interpolation method, is characterized in that, comprises the steps: Step S1, teaching the starting point P _s and the ending point _Pe of the swing welding path to obtain position and attitude information; Step S2, converting the welding path point attitude description into a quaternion representation; Step S3, calculate the quaternion attitude intermediate transformation Z _se of the starting point and the ending point; Step S4, calculating the normalization constant N _const of the intermediate attitude transformation Z _se ; Step S5, calculate the transformation angle φ of the quaternion transformation Z _se in the middle of the attitude; Step S6, calculate the attitude information of the ith interpolation point P _i from the welding path P _s to P _e ; then first calculate the attitude insertion angle of the interpolation point P _i

Then calculate the attitude information of the interpolation point _Pi ; Step S7, generate an attitude interpolation point, determine whether it is the end point, if so, the interpolation ends, otherwise return to step S6; Step S8, combining the spatial position interpolation information from the starting point to the end point of the welding path and the attitude interpolation information in step S7, the welding robot PLC controller converts the interpolation information into the corresponding joint angle information through the inverse solution calculation module, and passes The method of bus communication is sent to the robot actuator for execution. 2. The PLC-based welding robot weaving welding attitude interpolation method according to claim 1, wherein in the step S1, the starting point P _s and the ending point P _e of the welding path are taught, and the The position and attitude information P (x, y, z, α, β, γ) in the robot coordinate system; the position and attitude information of the robot is composed of the position vector (x, y, z) based on the rectangular space and the attitude vector ( α, β, γ) are described together. 3. the PLC-based welding robot weaving welding attitude interpolation method as claimed in claim 1, is characterized in that, in described step S2, Convert the attitude vectors of the starting points P _s and _Pe of the welding path to the quaternion space, then the attitude Z = [Z _w Z _x Z _y Z _z ] ^T can be described by the unit quaternion, and

The Euler angles are converted to quaternion formulas as follows:

4. the welding robot weaving welding posture interpolation method based on PLC as claimed in claim 1, is characterized in that, in step S3, calculates welding path starting point P _s to end point P _e intermediate transformation, comprising: Assuming that the attitude quaternions of the points P _s and Pe are Z _s and Z _e in turn _, and the intermediate transformation of the quaternions is Z _se , then:

From the properties of the identity matrix, it can be known that the inverse Z ^of the identity matrix is equal to its conjugate Z ^* , then the above formula can be further converted into the following formula:

5. PLC-based welding robot swing welding attitude interpolation method as claimed in claim 4, is characterized in that,

_Ze is:

Then the above _Ze and

Substitute into equation (3) to get the quaternion intermediate transformation Z _se :

6. PLC-based welding robot weaving welding attitude interpolation method as claimed in claim 1, is characterized in that, described calculating attitude intermediate transformation normalization constant N _const , comprises the steps: Suppose by

The obtained intermediate transformation quaternion Z _se is

Then the normalization constant N _const of the quaternion can be expressed by the following formula:

7. PLC-based welding robot weaving welding posture interpolation method as claimed in claim 1, is characterized in that, in described step S5, calculating intermediate transformation Z _se transformation angle φ, comprises the steps: The robot attitude rotation transformation can be described either by quaternion or by the axis-angle relationship, that is, the attitude transformation represented by the quaternion is expressed as the rotation axis defined by a unit vector

Rotate a certain angle φ, and the quaternion transformation angle can be obtained from the relationship between the quaternion and the three-dimensional rotation:

8. the welding robot weaving welding posture interpolation method based on PLC as claimed in claim 1, is characterized in that, described calculating welding path P _s to the intermediate interpolation point P _i of P _e posture change, comprises the steps: The attitude interpolation of the welding path starting point P _s to the ending point _Pe can be converted into an interpolation of the rotation angle φ of the intermediate transformation Z _se . Assuming that the number of swing interpolation of the welding path position is N, and the intermediate interpolation point i of the attitude is 1, 2, ..., (N-1); the information of the intermediate interpolation point P _i of the attitude is calculated as follows: a) Suppose the attitude change angle of the ith interpolation point relative to the welding starting point is

Then the first element of the quaternion pose transformation is:

b) Combined with the normalization constant of the intermediate transformation Z _se , the intermediate calculation variable κ can be obtained:

c) The attitude change quaternion Z _si of the intermediate attitude transformation interpolation point relative to the arc starting point can be expressed by the following formula:

Then the attitude quaternion Z _i of the interpolation point is: Z _i =Z _si ·Z _s d) Convert the attitude quaternion Z _i of the interpolation point P _i into Euler angles (RPY), assuming

The Euler angles of P _i are (α _i ,β _i ,γ _i ), then:

e) Repeat steps a to d until all the intermediate interpolation points are calculated; the last interpolation point is the end point P _e of the swing welding.

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