A comprehensive simulation method for welding robots

Abstract

The invention discloses a comprehensive simulation method for a welding robot, and relates to the technical field of mechanical manufacturing. The comprehensive simulation method for a welding robot of the invention comprises adopting SolidWorks to carry out modeling and importing it into ADAMS, performing kinematic simulation analysis on the robot, and then adopting the D-H parameter method to establish the relationship between each joint and the end, and obtaining the curve of the change of each joint angle over time, which provides assistance for the motor control of each joint axis in the future, and also provides important parameters for the trajectory planning of the end; in ADAMS, a fixed constraint is set for the base, and a translation pair and a rotation pair are set for the other joints, and a point drive command is applied at the end at the same time, and the rotation is applied as fixed, so as to truly simulate the actual scene.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical manufacturing, and more specifically to a comprehensive simulation method for a welding robot. Background Art

[0002] Large aerospace vehicles are generally large in size, weak in rigidity, and increasingly complex in structure. In large aluminum alloy spacecraft structures, there are a large number of complex welds, such as the intersection lines formed by spherical, cylindrical, truncated cone shells and circular and special-shaped flanges. Spacecraft manufacturing has requirements such as high quality, high reliability, high flexibility, high efficiency and low cost, so upgrading the manufacturing model is imminent.

[0003] As the welding tasks in the machinery manufacturing industry intensify, welding operations have poor working conditions and high heat radiation, making it a dangerous occupation. There are also many large-scale equipment in machinery manufacturing, which also increases the difficulty of welding. Welding robots are automatic mechanical equipment engaged in welding work. They can achieve precise welding for welds and put down just the right welding materials for filling. The efficiency is far higher than that of manual labor. Yuanfan Zeng (Zeng Y, Tian W, Liao W. Positional errors similarity analysis for error compensation of industrial robots [J]. Robotic and computer-integrated manufacturing 2016 (42): 113-120.) et al. studied the position error similarity of error compensation of industrial robots. Guanbin Gao (Zhao D, Dong C, Guo H, et al. Kinematic Calibration Based on the Multicollinearity Diagnosis of a 6-DOF Polishing Hybrid Robot Using a Laser Tracker [J]. Mathematical problems in engineering) et al. analyzed the structural parameters of a six-DOF industrial robot. Robotics will become an important part of social survival and industrial development, so robots have a promising research prospect. However, the manufacturing cycle of robots is long, the cost is high, and the design process is difficult to calculate. Therefore, it is extremely necessary to conduct 3D modeling and simulation analysis of welding robots before manufacturing. At present, many scholars have done a lot of work on this, but there are not many studies based on simulation. Summary of the invention

[0004] 1. Technical problem to be solved by the invention

[0005] In view of the problems of high design and manufacturing cost and long cycle of welding robots in the prior art, the present invention proposes a comprehensive simulation method for welding robots, which uses SolidWorks to build a model and imports it into ADAMS to perform kinematic simulation analysis on the robot, and then uses the DH parameter method to establish the relationship between each joint and the end. The robot is modeled and simulated by three-dimensional modeling software SolidWorks and dynamic simulation software ADAMS to obtain the change curve of each joint angle over time, which helps the subsequent motor control of each joint axis and also provides important parameters for the trajectory planning of the end.

[0006] 2. Technical solution

[0007] In order to achieve the above object, the technical solution provided by the present invention is:

[0008] A comprehensive simulation method for a welding robot adopts the DH parameter method to establish the relationship between each joint and the end, and models and simulates the robot through the three-dimensional modeling software SolidWorks and the dynamics simulation software ADAMS, which specifically includes the following steps:

[0009] Step 1: Use the modeling software SolidWorks to build a model of the welding robot;

[0010] Step 2: Define the material of the welding robot;

[0011] Step 3: Establish the DH parameters of the welding robot and derive the forward kinematics of the robot;

[0012] Step 4. Simplify the model established in step 1, and then import it into the dynamic simulation software ADAMS. Use the point drive provided in ADAMS to drive it. Set the base of the welding robot and the ground as a fixed joint, and the remaining joint types of the welding robot as translation joints and rotation joints, and add a drive function.

[0013] A further technical solution is that the welding robot includes a base fixedly connected to a ground reference, a first connecting rod is movably mounted on the base via a first joint, a second connecting rod is movably mounted on the outer end of the first connecting rod via a second joint, a third connecting rod is movably mounted on the outer end of the second connecting rod via a third joint, a fourth connecting rod is coaxially mounted inside the third connecting rod via a fourth joint, the outer end of the fourth connecting rod is externally connected to a fifth connecting rod via a fifth joint, and the outer end of the fifth connecting rod is movably mounted to a sixth connecting rod via a sixth joint.

[0014] Further technical solutions, in step 2, since the first three joints can send the end tool to different spatial positions, the requirements for materials are relatively high. Cast iron has high mechanical strength and toughness, and also has special properties such as heat resistance, corrosion resistance, and wear resistance. Therefore, the materials of the first joint, the second joint, and the third joint of the welding robot are defined as cast iron. The last three joints are mainly to meet the different requirements of the tool posture. In order not to affect the overall stability, aluminum materials are selected; because aluminum materials are light, soft, strong, and corrosion-resistant, the materials of the fourth joint, the fifth joint, and the sixth joint of the welding robot are defined as aluminum alloys to ensure that the simulated welding robot is close to the entity, thereby reflecting the real characteristics of the welding robot.

[0015] A further technical solution is that in step four, the simplification method is to delete structural features that have no effect on the simulation, such as screws, etc.; and it is necessary to ignore the friction force and coupling constraint equivalent transmission relationship, and then save the model in *.x_t format, and then import it into ADAMS. Since the welding robot assembly model established in SolidWorks is too complex and has too many parts, in order to perform accurate simulation in ADAMS, it is necessary to simplify the model and appropriately delete structural features that have no effect on the simulation.

[0016] According to a further technical solution, the base and the ground are fixed pairs; the first joint, the fourth joint and the fifth joint are rotation pairs; and the second joint, the third joint and the sixth joint are translation pairs.

[0017] Further technical solution, in step 3, it is assumed that the degree of freedom of the mechanical arm of the welding robot is n, and the mechanical arm is connected by n connecting rods and n-1 joints. In order to describe the relative position relationship between each connecting rod and the adjacent connecting rod, it is necessary to define a fixed coordinate system on each connecting rod. The fixed coordinate system is named according to the number of the fixed coordinate system. Therefore, the fixed coordinate system fixed on the connecting rod i is called the coordinate system {i}. Generally, the coordinate system {0} is defined to be fixed on the base, and then the DH coordinate system of the mechanical arm is established. The specific steps are as follows:

[0018] S1. Find the common perpendicular line ai between the joint axes i and i+1, and take the intersection of the joint axes i and i+1 or the intersection of the joint axis and the common perpendicular line as the origin of the link coordinate system {i};

[0019] S2. Definition of the intermediate position link coordinate system: The Z axis of the coordinate system {i} is called Zi, and coincides with the joint axis i. The origin is located at the intersection of the common vertical line ai and the joint axis i. Xi points from joint i to joint i+1 along the direction of ai.

[0020] S3. Definition of the first end link coordinate system: The coordinate system fixed on the base is the coordinate system {0}. Usually, Z0 is designated along the direction of joint axis 1. The right-hand orthogonal coordinate system (X0, Y0, Z0) is established according to the right-hand rule, where the X0 axis and the Y0 axis are perpendicular to the Z0 axis, and the direction is optional.

[0021] S4. Definition of the end link coordinate system: The Zn axis is parallel to the Zn1 axis of the link n-1 coordinate system and points to the outside direction of the robot body; the Xn axis is perpendicular to both the Zn1 axis and the Zn axis; the Yn axis is determined by the right-hand rule, thereby completing the establishment of the DH coordinate system of the robot arm.

[0022] A further technical solution is to establish the transformation of the coordinate system {i} relative to {i-1} according to the connecting rod coordinate system, that is,

[0023]

[0024] Where c represents the cosine trigonometric function, s represents the sine trigonometric function, and the forward kinematics of the robot arm can be obtained by multiplying the transformation matrices of each link:

[0025]

[0026] A further technical solution is to use the general point motion command to add a point drive command at the end of the robot, fix the three rotational pairs, that is, disp(time)=0*time, and define the remaining three translational pairs with the step function. Finally, set the simulation time and step size to complete the simulation. The form of the function STEP is STEP(x,x0,h0,x1,h1), where: x is the independent variable, x0 is the value of the independent variable at the starting point of the step function, h0 is the value of the function at the starting point of the step function, x1 is the value of the independent variable at the end of the step function, and h1 is the value of the function at the end of the step function.

[0027] 3. Beneficial effects

[0028] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0029] (1) A comprehensive simulation method for a welding robot of the present invention completes the design of welding robot parts and the coordination of assemblies based on SolidWorks, providing a model basis for ADAMS simulation; then the DH parameter method is used to establish the kinematic equation of the robot, describing the motion relationship between the joints and the relationship between the ends, and providing an important reference for the control and trajectory planning of the ends; at the same time, the welding robot can also be improved to complete other tasks, such as handling or palletizing, so as to achieve multi-purpose use of one machine and improve the value of the robot;

[0030] (2) In a comprehensive simulation method for a welding robot of the present invention, the welding robot assembly model established in SolidWorks is too complex and has too many parts. Therefore, in order to perform accurate simulation in ADAMS, it is necessary to simplify the model and appropriately delete structural features that have no effect on the simulation;

[0031] (3) A comprehensive simulation method for a welding robot of the present invention sets fixed constraints on the base in ADAMS, sets translational and rotational pairs for the other joints, and applies a point drive command at the end, and the rotation is applied as fixed, that is, disp(time)=0*time. The translational degree of freedom is defined according to the STEP function provided by ADAMS to truly simulate the actual scene;

[0032] (4) A comprehensive simulation method for a welding robot of the present invention has relatively high requirements on materials because the front three joints can send the end tool to different spatial positions. Cast iron has high mechanical strength and toughness, and also has special properties such as heat resistance, corrosion resistance, and wear resistance. Therefore, the material of the front three joints of the welding robot is defined as cast iron; and the rear three joints are mainly to solve the different requirements of the tool posture. In order not to affect the overall stability, aluminum material is selected because aluminum material is light, soft, strong and corrosion-resistant. Therefore, the material of the rear three joints of the welding robot is defined as aluminum alloy to ensure that the simulated welding robot is close to the entity, thereby reflecting the real characteristics of the welding robot. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A flow chart of the integrated simulation method for a receiving robot according to the present invention;

[0034] Figure 2 It is a schematic diagram of the three-dimensional structure of the receiving robot of the present invention.

[0035] In the figure: 1-base; 2-first joint; 3-first connecting rod; 4-second joint; 5-second connecting rod; 6-third joint; 7-third connecting rod; 8-fourth joint; 9-fourth connecting rod; 10 fifth joint; 11-fifth connecting rod; 12-sixth joint; 13-sixth connecting rod. DETAILED DESCRIPTION

[0036] In order to further understand the content of the present invention, the invention is described in detail with reference to the accompanying drawings.

[0037] Example 1

[0038] A comprehensive simulation method for a welding robot in this embodiment is as follows: Figure 1As shown in the figure, the relationship between each joint and the end is established by using the DH parameter method, and the robot is modeled by using the 3D modeling software SolidWorks and the dynamics simulation software ADAMS, which specifically includes the following steps:

[0039] Step 1: Use the modeling software SolidWorks to build a model of the welding robot;

[0040] Step 2: Define the material of the welding robot;

[0041] Step 3: Establish the DH parameters of the welding robot and derive the forward kinematics of the robot;

[0042] Step 4: Simplify the model established in step 1, and then import it into the dynamic simulation software ADAMS. Use the point drive provided in ADAMS to drive it. Set the base 1 of the welding robot and the ground as a fixed joint, and the remaining joint types of the welding robot as translation joints and rotation joints, and add a drive function.

[0043] In this embodiment, since it is difficult to model directly in ADAMS, the third-party modeling software SolidWorks is used to build a model of the welding robot, which provides a model basis for ADAMS simulation; by performing accurate simulation in ADAMS, the curve of the change of each joint angle over time is obtained, which helps the motor control of each joint axis in the future, and also provides important parameters for the trajectory planning of the terminal. At the same time, the welding robot can also be improved to complete other tasks, such as handling or palletizing, so as to achieve multi-purpose use of one machine and improve the value of the robot.

[0044] Example 2

[0045] The welding robot comprehensive simulation method of this embodiment has the same basic structure as that of embodiment 1, and the differences and improvements are as follows: Figure 2 As shown, the welding robot includes a base 1 fixedly connected to a ground reference, a first connecting rod 3 is movably mounted on the base 1 through a first joint 2, a second connecting rod 5 is movably mounted on the outer end of the first connecting rod 3 through a second joint 4, a third connecting rod 7 is movably mounted on the outer end of the second connecting rod 5 through a third joint 6, a fourth connecting rod 9 is coaxially mounted inside the third connecting rod 7 through a fourth joint 8, the outer end of the fourth connecting rod 9 is externally connected to a fifth connecting rod 11 through a fifth joint 10, and the outer end of the fifth connecting rod 11 is movably mounted to a sixth connecting rod 13 through a sixth joint 12.

[0046] In step 2, since the first three joints can send the end tool to different spatial positions, the requirements for materials are relatively high. Cast iron has high mechanical strength and toughness, and has special properties such as heat resistance, corrosion resistance, and wear resistance. Therefore, the materials of the first joint 2, the second joint 4, and the third joint 6 of the welding robot are defined as aluminum. The last three joints are mainly to meet the different requirements of the tool posture. In order not to affect the overall stability, cast iron materials are selected; because aluminum materials are light, soft, strong, and corrosion-resistant, the materials of the fourth joint 8, the fifth joint 10, and the sixth joint 12 of the welding robot are defined as aluminum alloy to ensure that the simulated welding robot is close to the entity, thereby reflecting the real characteristics of the welding robot.

[0047] In step 4, the simplified method is to delete the structural features that have no effect on the simulation, and do not consider the equivalent transmission relationship of friction and coupling constraints. Then save the model in *.x_t format and import it into ADAMS. The base 1 and the ground are fixed joints; the first joint 2, the fourth joint 8 and the fifth joint 10 are rotation joints; the second joint 4, the third joint 6 and the sixth joint 12 are translation joints.

[0048] Example 3

[0049] A welding robot comprehensive simulation method of this embodiment has the same basic structure as that of embodiment 2, except that: in step 3, it is assumed that the degree of freedom of the mechanical arm of the welding robot is n, and the mechanical arm is connected by n connecting rods and n-1 joints. The fixed coordinate system fixed to the connecting rod i is called the coordinate system {i}. Generally, the coordinate system {0} is defined to be fixed on the base 1, and then the DH coordinate system of the mechanical arm is established. The specific steps are as follows:

[0050] S1. Find the common perpendicular line ai between the joint axes i and i+1, and take the intersection of the joint axes i and i+1 or the intersection of the joint axis and the common perpendicular line as the origin of the link coordinate system {i};

[0051] S2. Definition of the intermediate position link coordinate system: The Z axis of the coordinate system {i} is called Zi, and coincides with the joint axis i. The origin is located at the intersection of the common vertical line ai and the joint axis i. Xi points from joint i to joint i+1 along the direction of ai.

[0052] S3. Definition of the first end link coordinate system: The coordinate system fixed on the base 1 is the coordinate system {0}. Usually, Z0 is designated along the direction of the joint axis 1. The right-hand orthogonal coordinate system (X0, Y0, Z0) is established according to the right-hand rule, where the X0 axis and the Y0 axis are perpendicular to the Z0 axis, and the direction is optional;

[0053] S4. Definition of the end link coordinate system: The Zn axis is parallel to the Zn1 axis of the link n-1 coordinate system and points to the outside direction of the robot body; the Xn axis is perpendicular to both the Zn1 axis and the Zn axis; the Yn axis is determined by the right-hand rule, thereby completing the establishment of the DH coordinate system of the robot arm.

[0054] According to the connecting rod coordinate system, the transformation of coordinate system {i} relative to {i-1} is established, that is,

[0055]

[0056] Where c represents the cosine trigonometric function, s represents the sine trigonometric function, and the forward kinematics of the robot arm can be obtained by multiplying the transformation matrices of each link:

[0057]

[0058] In this embodiment, it is assumed that the degree of freedom of the robotic arm of the welding robot is n, and the robotic arm is connected by n connecting rods and n-1 joints. The configuration parameters of the robotic arm of the welding robot are established according to the DH coordinate system as shown in Table 1.

[0059] Table 1

[0060] Joint number i <![CDATA[α i-1 ]]> <![CDATA[a i-1 ]]> <![CDATA[θ i ]]> <![CDATA[d i ]]> <![CDATA[Joint θ i Range]]> Connecting rod size / mm 1 0° 0 90° 0 -170° to 170° 2 90° a1 0 0 -80° to 110° a1＝160 3 0° a2 0 0 -60° to 70° a2＝560 4 90° a3 0 d4 -170° to 170° a3=130d4=160 5 -90° 0 0 0 -90° to 130° 6 90° 0 0 0 -350° to 350°

[0061] Example 4

[0062] A comprehensive simulation method for a welding robot in this embodiment has the same basic structure as that in Embodiment 3, but the differences and improvements are as follows: a point drive command is added to the end of the robot using a general point motion command, the three rotation pairs are fixed, that is, disp(time)=0*time, and the remaining three translation pairs are defined by a step function. Finally, the simulation time and step size are set to complete the simulation.

[0063] In this embodiment, the form of the function STEP is STEP(x, x0, h0, x1, h1), where: x is the independent variable, x0 is the value of the independent variable at the starting point of the step function, h0 is the value of the function at the starting point of the step function, x1 is the value of the independent variable at the end point of the step function, and h1 is the value of the function at the end point of the step function.

[0064] The translational degrees of freedom for x, y, and z are defined as follows:

[0065] Tra X: step(time, 0, 0, 4, -535) + step (time, 4, 0, 8, 300);

[0066] Tra Y: step(time, 0, 0, 4, 0) + step (time, 4, 0, 8, 300);

[0067] Tra X: step(time, 0, 0, 4, 0) + step (time, 4, 0, 8, 300).

[0068] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A comprehensive simulation method for a welding robot, characterized in that: The DH parameter method is used to establish the relationship between each joint and the end. The robot is modeled and simulated using the 3D modeling software SolidWorks and the dynamics simulation software ADAMS. The specific steps include: Step 1: Use the modeling software SolidWorks to build a model of the welding robot; Step 2: Define the material of the welding robot; Step 3: Establish the DH parameters of the welding robot and derive the forward kinematics of the robot; Step 4: simplify the model established in step 1, import it into the dynamic simulation software ADAMS, drive it using the point drive provided in ADAMS, set the base (1) of the welding robot and the ground as a fixed pair, set the other joint types of the welding robot as translation pairs and rotation pairs, and add a drive function; the welding robot comprises a base (1) fixedly connected to a ground reference, a first connecting rod (3) movably mounted on the base (1) through a first joint (2), a second connecting rod (5) movably mounted on the outer end of the first connecting rod (3) through a second joint (4), a third connecting rod (7) movably mounted on the outer end of the second connecting rod (5) through a third joint (6), a fourth connecting rod (9) coaxially mounted inside the third connecting rod (7) through a fourth joint (8), the outer end of the fourth connecting rod (9) is externally connected to a fifth connecting rod (11) through a fifth joint (10), and the outer end of the fifth connecting rod (11) is movably mounted to a sixth connecting rod (13) through a sixth joint (12); In step 2, the material of the first joint (2), the second joint (4) and the third joint (6) of the welding robot is defined as cast iron; the material of the fourth joint (8), the fifth joint (10) and the sixth joint (12) of the welding robot is defined as aluminum alloy; In step 4, the simplification method is to delete the structural features that have no effect on the simulation, and not consider the equivalent transmission relationship of friction and coupling constraints. Then save the model in *.x_t format and import it into ADAMS. Use the general point motion command to add a point drive command to the end of the robot, fix the three rotation joints, that is, disp(time)=0*time, and define the remaining three translation joint degrees of freedom with the step function. Finally, set the simulation time and step size. The form of the function STEP is STEP(x,x0,h0,x1,h1), where: x is the independent variable, x0 is the value of the independent variable at the starting point of the step function, h0 is the value of the function at the starting point of the step function, x1 is the value of the independent variable at the end point of the step function, and h1 is the value of the function at the end point of the step function.

2. A welding robot comprehensive simulation method according to claim 1, characterized in that: The base (1) and the ground form a fixed pair; the first joint (2), the fourth joint (8) and the fifth joint (10) form a rotation pair; and the second joint (4), the third joint (6) and the sixth joint (12) form a translation pair.

3. A welding robot comprehensive simulation method according to claim 2, characterized in that: In step 3, it is assumed that the degree of freedom of the mechanical arm of the welding robot is n, and the mechanical arm is connected by n connecting rods and n-1 joints. The fixed coordinate system fixed on the connecting rod i is called the coordinate system {i}. Generally, the coordinate system {0} is defined to be fixed on the base (1), and then the DH coordinate system of the mechanical arm is established. The specific steps are as follows: S1. Find the common perpendicular line ai between the joint axes i and i+1, and take the intersection of the joint axes i and i+1 or the intersection of the joint axis and the common perpendicular line as the origin of the link coordinate system {i}; S2. Definition of the intermediate position link coordinate system: The Z axis of the coordinate system {i} is called Zi, and coincides with the joint axis i. The origin is located at the intersection of the common vertical line ai and the joint axis i. Xi points from joint i to joint i+1 along the direction of ai. S3. Definition of the first end link coordinate system: The coordinate system fixed on the base (1) is the coordinate system {0}. Usually, Z0 is designated along the direction of the joint axis 1. The right-hand orthogonal coordinate system (X0, Y0, Z0) is established according to the right-hand rule, where the X0 axis and the Y0 axis are perpendicular to the Z0 axis, and the direction is optional. S4. Definition of the end link coordinate system: The Zn axis is parallel to the Zn1 axis of the link n-1 coordinate system and points to the outside direction of the robot body; the Xn axis is perpendicular to both the Zn1 axis and the Zn axis; the Yn axis is determined by the right-hand rule, thereby completing the establishment of the DH coordinate system of the robot arm.

4. A welding robot comprehensive simulation method according to claim 3, characterized in that: According to the connecting rod coordinate system, the transformation of coordinate system {i} relative to {i-1} is established, that is, Where c represents the cosine trigonometric function, s represents the sine trigonometric function, and the forward kinematics of the robot arm can be obtained by multiplying the transformation matrices of each link:

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