A layer-by-layer joint trajectory optimization method and device for 6-axis 3D printing

Abstract

The present invention discloses a layer-by-layer joint trajectory optimization method and device for 6-axis 3D printing, comprising the following steps: obtaining the total number of layers printed and the printing path of each layer when printing an object layer by layer, wherein the printing path includes multiple path points; using the angle at which the end of the 6-axis 3D printer's robotic arm rotates around the Z axis of the robotic arm reference coordinate system when printing each path point of each layer as a variable to be optimized, and determining an expression for the variable to be optimized; determining an inverse kinematics model of the printer's robotic arm and solving the model to obtain a relationship between the rotation angle of each axis of the 6-axis 3D printer and the variable to be optimized; determining an optimization objective function based on the relationship and the expression of the variable to be optimized, setting robotic arm axis limit constraints and robotic arm singularity constraints for the optimization objective function; and determining the optimized rotation angle of each axis of the 6-axis 3D printer during printing based on the optimization objective function, the constraints, and the angle relationship. The present invention can improve printing quality and efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of industrial manufacturing technology, and specifically relates to a layer-by-layer joint trajectory optimization method and equipment for 6-axis 3D printing. Background Art

[0002] Additive manufacturing (AM) or three-dimensional (3D) printing has been developing continuously since its birth in the 1980s. Additive manufacturing is manufactured by continuously depositing materials layer by layer along the path generated by the computer-aided design (CAD) model. Multi-axis support-free additive manufacturing has broad application prospects in aerospace, energy equipment, automobiles and ships due to its characteristics of realizing the manufacturing of arbitrarily complex parts. Traditional additive manufacturing systems are all 2.5 or 3+2 axis printing configurations. This configuration usually requires support structures and produces a step effect. The method of fixing the print head, moving the printing platform and keeping the material always below the deposition point is adopted. This multi-axis printing method can reduce support structures, reduce the step effect, and realize the manufacturing of complex parts. However, in a strict industrial production environment, AM still has the following limitations:

[0003] First, the robot arm singularity points and joint limits: The robot arm trajectory calculated by inverse kinematics from the printing trajectory may have singularity points and exceed the joint limits, which will cause the robot arm movement process to be discontinuous, affecting the printing quality and efficiency.

[0004] Second, the joint displacement of the robotic arm is large: the joint displacement of the robotic arm trajectory calculated by inverse kinematics may be large. Traditional optimization methods are all aimed at globally optimizing the robotic arm trajectory, and are more targeted at traditional printing methods. Axis redundancy is not considered, resulting in large displacement of the robotic arm movement, affecting printing quality and efficiency. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a layer-by-layer joint trajectory optimization method and device for 6-axis 3D printing.

[0006] The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0007] The present invention provides a layer-by-layer joint trajectory optimization method for 6-axis 3D printing, comprising:

[0008] Obtaining the total number of layers required to print the object to be printed layer by layer and the printing path of each layer, wherein the printing path of each layer includes multiple path points to be printed, the tangent direction of the surface at each path point is the printing direction of the path point, and the coordinates of each path point are three-dimensional coordinates in the coordinate system of the object to be printed;

[0009] When printing each path point of each layer, the end of the robotic arm of the 6-axis 3D printer rotates around the Z axis of the reference coordinate system by an angle R Z as a variable to be optimized, and determining an expression of the variable to be optimized according to the coordinates of each path point in the printing path of each layer;

[0010] Determine the inverse kinematics model of the manipulator of the 6-axis 3D printer and solve the inverse kinematics model of the manipulator to obtain the rotation angle of each axis of the 6-axis 3D printer and the angle R Z The angular relationship between

[0011] Determining an optimization objective function based on the angle relationship and the expression of the variable to be optimized, and setting a robot arm axis limit constraint condition and a robot arm singular point constraint condition for the optimization objective function;

[0012] Based on the optimization objective function, the robot arm axis limit constraint condition, the robot arm singular point constraint condition and the angle relationship, the optimized rotation angle of each axis of the 6-axis 3D printer when printing each path point of each layer is determined.

[0013] The present invention also provides a 6-axis 3D printing layer-by-layer joint trajectory optimization device, comprising a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other via the communication bus;

[0014] The memory is used to store computer programs;

[0015] The processor is used to implement the steps of the above-mentioned 6-axis 3D printing layer-by-layer joint trajectory optimization method when executing the program stored in the memory.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention takes into account the influence of robot arm movement on printing quality and efficiency, utilizes the redundancy of one axis in six-axis supportless printing, designs optimization variables and objective functions, and adds robot arm joint limit constraints and robot arm singular point constraints to the objective function. Then, the optimization variables are solved, and the trajectory of each axis of the six-axis supportless printer is optimized according to the solved optimization variables. Singular points and joint limits can be avoided, and the robot arm joint displacement can be reduced, thereby improving printing quality and printing efficiency.

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the structure of a 6-axis 3D printer;

[0020] Figure 2 3D printing is a flowchart of a layer-by-layer joint trajectory optimization method for 6-axis 3D printing provided by an embodiment of the present invention;

[0021] Figure 3 It is a principle diagram of the variable layer height method;

[0022] Figure 4 This is a schematic diagram of a hemispherical thin-walled body of revolution sliced ​​horizontally;

[0023] Figure 5 It is a principle diagram of the fixed chord error method;

[0024] Figure 6 Yes Figure 4 The schematic diagram of the effect of the path points of each layer obtained by longitudinally slicing each horizontal plane of the hemispherical thin-walled body of revolution after horizontal slicing is shown;

[0025] Figure 7 This is a flow chart of a layer-by-layer joint trajectory optimization method for 6-axis 3D printing of thin-walled rotational parts provided by an embodiment of the present invention;

[0026] Figure 8 This is a comparison diagram of the effects before and after optimization provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0028] The optimization method of the present invention is applicable to a 6-axis 3D printer and is used to optimize the trajectories (also known as rotation angles) of the 6 axes (also known as 6 joints) of the 6-axis 3D printer. Figure 1 This is a schematic diagram of the structure of a 6-axis 3D printer, wherein 1 is a printing platform, and 2, 3, 4, 7, 8, and 9 are the 6 axes of the robotic arm, and 5 is a printer frame, wherein the print head 6 is directed vertically downward and is fixed and cannot move or rotate. The printing platform 1 is fixed to the end of the 6-axis robotic arm and moves and rotates with the movement and rotation of the end of the 6-axis robotic arm. The printed object is always located below the print head 6 and on the printing platform 1, realizing support-free printing. For the support-free printing, only five degrees of freedom are required. The end of the 6-axis 3D printer has six degrees of freedom, so there is always one degree of freedom redundancy, namely the rotation of the printing platform around the axis of the print head. Therefore, the present invention uses axis redundancy to optimize the trajectory of the robotic arm.

[0029] Figure 2 FIG. 1 is a flow chart of a layer-by-layer joint trajectory optimization method for 6-axis 3D printing provided by an embodiment of the present invention, such as Figure 2 As shown, the method includes:

[0030] S101. Obtain the total number of layers required to print the object to be printed layer by layer and the printing path of each layer, wherein the printing path of each layer includes multiple path points to be printed, the tangent direction of the surface at each path point is the printing direction of the path point, and the coordinates of each path point are three-dimensional coordinates in the coordinate system of the object to be printed.

[0031] Here, the coordinate system of the object to be printed is a coordinate system with the center of the object to be printed as the origin, the horizontal plane where the bottom surface of the object to be printed is located as the XY plane, the X axis and the Y axis are perpendicular to each other, and the direction perpendicular to the XY plane is the Z axis direction.

[0032] S102: When printing each path point of each layer, the angle R of the end of the 6-axis 3D printer's mechanical arm rotates around the Z axis of the reference coordinate system. Z As the variable to be optimized, the expression of the variable to be optimized is determined according to the coordinates of each path point in the printing path of each layer.

[0033] Here, the reference coordinate system is the coordinate system that translates the robot arm base coordinate system to the coordinate origin of the robot arm end coordinate system; the robot arm base coordinate system is a three-dimensional coordinate system with the center of the robot arm base as the origin, the horizontal plane where the robot arm base is located as the XY plane, the X-axis and Y-axis are perpendicular to each other, and the direction perpendicular to the XY plane is the Z-axis direction; the robot arm end coordinate system is a three-dimensional coordinate system with the center point of the robot arm end as the origin, the surface where the top surface of the robot arm end is located as the XY plane, and the direction perpendicular to the XY plane as the Z-axis direction.

[0034] S103, determine the inverse kinematics model of the robot arm of the 6-axis 3D printer, and solve the inverse kinematics model of the robot arm to obtain the rotation angle and angle R of each axis of the 6-axis 3D printer Z The angle relationship between them.

[0035] S104 , determining an optimization objective function based on the angle relationship and the expression of the variable to be optimized, and setting a robot arm axis limit constraint condition and a robot arm singular point constraint condition for the optimization objective function.

[0036] Here, the robot arm axis limits refer to the maximum angles of the six axes of a 6-axis 3D printer. By using the robot arm axis limit constraints, the present invention ensures that each axis of the 6-axis 3D printer reaches the target position when printing each path point, while also ensuring that the rotation angle of each axis does not exceed the preset maximum angle. A robot arm singularity refers to a singular state position during robot arm motion, which can cause the robot to stop moving, resulting in discontinuous motion speed and, in turn, poor performance of the printed object. By using the robot arm singularity constraints, the present invention prevents singularities in robot arm motion during printing in a 6-axis 3D printer, thereby improving the quality of printed objects.

[0037] S105 , based on the optimization objective function, the robot arm axis limit constraints, the robot arm singular point constraints, and the angle relationship, determine the optimized rotation angle of each axis of the 6-axis 3D printer when printing each path point of each layer.

[0038] Regarding the above-mentioned S101, the total number of layers required to print the object and the printing path for each layer can be directly obtained from the outside world, or the total number of layers required to print the object and the printing path for each layer can be determined based on the object. For example, when the object to be printed is a thin-walled rotating object, the method described in the following steps S11 to S13 can be used to obtain the total number of layers required to print the object and the printing path for each layer.

[0039] S11. Determine the geometric model of the thin-walled body of revolution.

[0040] Here, the geometric model of the thin-walled revolution body can be determined according to the equation of the thin-walled revolution body.

[0041] S12. Slice the geometric model in the horizontal direction to divide the geometric model into multiple horizontal layers, and obtain the total number of layers required for printing the thin-walled rotational body layer by layer.

[0042] Here, the variable layer height method can be used to slice the geometric model horizontally. Specifically, Figure 3 As shown, the busbar length (also called busbar distance) of each horizontal layer is the preset value Δ layer , according to the arc length formula, the central angle can be obtained R is the radius of the thin-walled body of revolution. When the geometric model is sliced ​​horizontally, the central angle of the Lth layer is In this way, a cutting origin can be obtained for each layer, for example, Figure 3 The point c in the figure is the cutting origin of the first layer. After that, horizontal cutting is performed starting from the cutting origin to divide the geometric model into C horizontal layers with different spacings along the horizontal direction. That is, the total number of layers when printing the thin-walled rotational body is C, where L = 1, 2, ..., C. For example, Figure 4 This is a schematic diagram of a horizontal slice of a hemispherical thin-walled rotating body. Figure 4 The yellow line in the figure is the axis of the thin-walled body of revolution, and the red line is the arc length of a horizontal layer.

[0043] S13. Slice each horizontal layer longitudinally to determine the path points that need to be printed when printing each horizontal layer and the three-dimensional coordinates of each path point in the coordinate system of the object to be printed, wherein all the path points that need to be printed when printing a horizontal layer constitute the printing path of the horizontal layer.

[0044] Here, after obtaining C horizontal layers, for each horizontal layer, the fixed chord error method can be used to plan the printing path of the horizontal layer. Specifically, the surface of each horizontal layer is a circle, such as Figure 5 As shown, we can use the formula Calculate the central angle θ, where R' is the radius of the circle, c is the chord error, and c is a preset fixed value. θ represents the central angle between two adjacent path points of the slice layer. Thus, the central angle between the first path point and the second path point of the slice layer is 2θ, the central angle between the first path point and the third path point of the slice layer is 4θ, and the central angle between the first path point and the fourth path point of the slice layer is 6θ. By analogy, all the path points on the slice layer and the three-dimensional coordinates of each path point in the coordinate system of the thin-walled rotation body can be obtained, and the total number of path points on the slice layer is 2θ. All the path points on the slice layer constitute the printing path of the slice layer; the coordinate system of the thin-walled rotation body is a coordinate system with the center of the thin-walled rotation body as the origin, the horizontal plane where the bottom surface of the thin-walled rotation body is located as the XY plane, and the direction perpendicular to the XY plane as the Z axis direction. For example, Figure 6 Yes Figure 4 The schematic diagram of the effect of the path points of each layer obtained by longitudinally slicing each horizontal plane of the hemispherical thin-walled rotational body after horizontal slicing is shown.

[0045] Traditional additive manufacturing methods use a method that intersects parallel planes or offset surfaces with the model, regardless of the part's shape. This rigid layering method can lead to a stair-stepping effect on the surface, affecting the part's precision and surface quality. The present invention applies this layering method to thin-walled bodies of revolution, eliminating or significantly reducing this stair-stepping effect, resulting in a smoother surface quality.

[0046] Here, for the above S102, the angle R Z The reasons for choosing variables to be optimized are as follows:

[0047] Considering the support-free printing method, the printing direction of each path point in each layer is the tangent direction of the surface at that printing point. This direction determines the posture of the end of the robotic arm of the 6-axis 3D printer. The core of the support-free printing method is to fix the printing platform to the end of the robotic arm and move and rotate it accordingly, while the print head is fixed so that the printing target is always located below the print head. Therefore, the printing direction of each path point is required to be collinear with the axial direction of the print head, which can be expressed as in,

[0048] M Robot→part Represents the posture rotation matrix of the end of the manipulator, that is, the end of the manipulator rotates around the Z, Y, and X axes of the manipulator base coordinate system in sequence, R X 、R Y and R Z They represent the angles at which the end of the 6-axis 3D printer's robotic arm rotates around the X-axis, Y-axis, and Z-axis of the reference coordinate system when printing each path point of each layer. is the printing direction of the i-th path point in the L-th layer, L=1,2,...,C, i=1,2,...,N L , is the axial direction of the print head, is the Z-axis direction of the robot arm base coordinate system. By setting the printing direction of each path point to be collinear with the axis of the print head, the object being printed can rotate freely around the tool axis of the print head. That is, the end of the robot arm of the 6-axis 3D printer can rotate around the axis of the print head during printing. Therefore, the above formula We can get the equation Solving the equation gives R X With R Z The relationship between R Y With R Z The relationship between them is as follows: X =arctan(S X ,C X ), S X =(b Y ×cosR Z +b X ×sinR Z ),

[0049] R Y =arctan(S Y ,C Y ),

[0050] S Y =(bX ×cosR Z +b Y ×sinR Z ), C Y =b Z ; Among them, b X 、b Y and b Z Represents the X, Y, and Z components of the printing direction of each path point of each layer in the robot end coordinate system. X With R Y Both can be obtained by R Z Therefore, R Z as the variable to be optimized.

[0051] In the present invention, the expression of the variable to be optimized is as follows:

[0052]

[0053] θ L,i =arctan2(Y L,i ,X L,i );

[0054] in, is the variable to be optimized, The angle R that the end of the 6-axis 3D printer's robotic arm rotates around the Z axis of the reference coordinate system when printing the i-th path point of the L-th layer Z , L=1,2,...,C, i=1,2,...,N L , n is the preset value, and n represents the order, Y L,i is the y coordinate value of the i-th path point in the L-th layer, X L,i is the x-coordinate value of the i-th path point in the L-th layer, A L,n Represents the matrix of coefficients to be optimized, A L,n Each element in is a coefficient to be optimized. Here, n can be set according to actual needs. The larger the value of n, the more accurate the optimized variable.

[0055] In the present invention, when printing each path point of each layer, the posture M of the end of the robotic arm of the 6-axis 3D printer is determined by the coordinates of the print head of the 6-axis 3D printer in the coordinate system of the robotic arm base and the coordinates of the path point. The expression of the posture M is as follows:

[0056]

[0057] Among them, X Tool 、Y Tool and Z Tool Indicates the coordinates of the print head in the robot base coordinate system, XL,i 、Y L,i and Z L,i Represents the coordinates of the i-th path point in the L-th layer.

[0058] Here, the expression of the inverse kinematics model of the 6-axis 3D printer robot arm is where n x 、n y and n z Represents the cosine of the three directions of the x-axis of the robot arm end coordinate system to the X, Y, and Z axes of the robot arm base coordinate system, o x 、o y and o z Represents the cosine of the y-axis of the robot end coordinate system to the X, Y, and Z-axis of the robot base coordinate system, a x 、a y and a z represents the cosine of the z-axis of the robot end coordinate system to the X, Y, and Z axes of the robot base coordinate system; p x 、p y and p z Represents the coordinate components of the X, Y, and Z axes of the robot arm end coordinate system in the robot arm base coordinate system, M 01 , M 12 , M 23 , M 34 , M 45 , M 56 Represents the coordinate transformation matrix between each joint coordinate system, for example, M 01 Represents the coordinate transformation matrix between the robot base coordinate system and the first joint coordinate system, M 12 Represents the coordinate transformation matrix between the first joint coordinate system and the second joint coordinate system. Each joint coordinate system is the coordinate system of each axis. The joint coordinate system is flexible and has a specific setting method. For example, it can be a three-dimensional coordinate system with the center point of the joint as the origin, the plane where the origin is located as the XY plane, and the direction perpendicular to the XY plane as the Z axis.

[0059] By solving the inverse kinematics model of the robot arm, the rotation angle q of the j-th axis of the 6-axis 3D printer when printing each path point of each layer can be obtained. j With angle R Z The angle relationship between them, where j = 1 to 6. The expression of this angle relationship is:

[0060]

[0061]

[0062]

[0063] q2=q23-q3;

[0064] q4=arctan2(-axs1+ayc1,-axc1c23-ays1c23+azs23);

[0065] q5=arctan2(s5,c5);

[0066] q6=arctan2(s6,c6);

[0067]

[0068] s5=-ax(c1c23c4+s1s4)-ay(s1c23c4-s1s4)+az(s23c4);

[0069] c5=ax(-s23c1)+az(-c23)+ay(-s1s23);

[0070] s6=-nx(c1c23s4-s1c4)-ny(s1c23s4+c1c4)+nz(s23s4);

[0071] Among them, c1 represents cos(q1), c12 represents cos(q1+q2), and the rest are similar; s1 represents sin(q1), s23 represents sin(q2+q3), and the rest are similar; a2 represents the distance between Z2 and Z3, a3 represents the distance between Z3 and Z4, d3 represents the distance between X3 and X2, and d4 represents the distance between X4 and X3, among which Z2 refers to the Z axis of the second joint coordinate system, and the rest are similar; X2 refers to the X axis of the second joint coordinate system, and the rest are similar, and will not be repeated here.

[0072] Obviously, q j It is R Z Here, the solution method can adopt the existing method, which will not be described in detail in the present invention.

[0073] In the present invention, the expressions of the optimization objective function, the robot axis limit constraint condition, and the robot arm singular point constraint condition are as follows:

[0074]

[0075]

[0076]

[0077] Among them, Φ(q(R Z )) represents the optimization objective function, Ψ jrepresents the limit constraint of the robot axis, Ψ7 represents the singular point constraint of the robot arm, j represents the j-th axis of the 6-axis 3D printer, j=1,2,...,6, represents the weighted value of the j-th axis, q i,j represents the rotation angle of the j-th axis of the 6-axis 3D printer when printing the i-th path point of the L-th layer, represents the average angle of the j-th axis, is the maximum rotation angle of the j-th axis, is the minimum rotation angle of the j-th axis, is the travel of the j-th axis, Make j If the value of is less than 0, the position of the j-th axis will be within the limit when printing each path point. minλ represents the minimum value in λ, maxλ represents the maximum value in λ, and λ represents the matrix J(q)×J Τ (q), J(q) represents the Jacobian matrix of the six-axis robotic arm of the six-axis 3D printer, which reflects the relationship between the differential motion of the robotic arm end coordinate system and the differential motion of each joint, Ψ max is the preset value, max It can be determined based on actual experience; making the value of Ψ7 less than or equal to 0 can avoid singular point positions in the movement of the robot arm during the printing of each path point.

[0078] In the present invention, the above S105 can be implemented by the following steps:

[0079] S1051. Based on the robot arm axis limit constraints and the robot arm singular point constraints, solve the optimization objective function to obtain the optimized angle R when printing each path point of each layer. Z .

[0080] Here, when solving the optimization objective function, a variety of solutions can be used. For example, the "fmincon" function can be used in Matlab to solve the optimization objective function to solve the problem of printing the i-th path point of the L-th layer. Afterwards, Substitution The time required to print the i-th path point of the L-th layer can be calculated. Here, the calculated is to optimize the objective function Φ(q(R Z ))The smallest Moreover, the Satisfy the robot arm axis limit constraints and robot arm singular point constraints.

[0081] S1052, according to the optimized angle R Z The optimized rotation angle of each axis of the 6-axis 3D printer when printing each path point of each layer is obtained by the relationship between the rotation angle and the angle.

[0082] Here, in getting Afterwards, you can Substituting this into the angle relationship expression, we can obtain the rotation angle of the j-th axis of the 6-axis 3D printer when printing the i-th path point of the L-th layer. In this way, we can obtain the trajectory of the j-th axis of the 6-axis 3D printer when printing the i-th path point of the L-th layer. After that, we can print according to the trajectory of the j-th axis of the 6-axis 3D printer when printing the i-th path point of the L-th layer, thereby printing out the corresponding object.

[0083] In one example, Figure 7 It is a layer-by-layer joint trajectory optimization process for 6-axis 3D printing of thin-walled rotational parts. Figure 7 As shown, the equation of the thin-walled rotating part is first determined, and then the geometric model of the thin-walled rotating part is determined based on the equation. Then, a printing path is generated based on the geometric model of the thin-walled rotating part. Specifically, when generating the printing path, the geometric model is first sliced ​​horizontally using a variable layer height method, and then each horizontal layer obtained by slicing is sliced ​​vertically, thereby obtaining the path points required for printing each horizontal layer. The path points required for printing each horizontal layer constitute the printing path of the layer, and then the printing direction of each path point is determined. Then, a corresponding nonlinear constraint optimization model is established based on the path points. Specifically, the expressions of the variables to be optimized, the robot axis limit constraint equations and the robot arm singular point constraint equations, and the optimization objective function are respectively established; then, MATLAB is used to solve the optimization objective function to obtain the solution result. Then, based on the solution result, the optimized rotation angle of each axis of the 6-axis 3D printer is generated when printing each path point of each layer of the thin-walled rotating part, thereby obtaining the optimal joint trajectory of the 6-axis 3D printer when printing each path point of each layer of the thin-walled rotating part.

[0084] The following is based on Figure 8 The technical effect of the optimization method provided by the present invention is further explained. Assuming n=1, the i-th path point in the L-th layer has α L,1 and α L,0 , according to the α of each layer L,1 and α L,0 , obtain the optimized robot arm joint trajectory, and draw a comparison α L,1 and α L,0 The joint trajectory of the robotic arm at this time is as follows Figure 8 As shown, Figure 8The six figures in the figure respectively represent the angles of each joint of the robotic arm corresponding to the path points during the printing process, wherein the horizontal axis represents the path point sequence and the vertical axis represents the joint angle. As shown in the figure, after optimization using the optimization method of the present invention, the joint trajectory is superior to the trajectory before optimization in terms of displacement, singular point avoidance, etc.

[0085] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0086] In the description of this specification, the reference terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" mean that the specific features or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0087] In the specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple situations. Certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0088] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A layer-by-layer joint trajectory optimization method for 6-axis 3D printing, characterized in that: include: Obtaining the total number of layers required to print the object to be printed layer by layer and the printing path of each layer, wherein the printing path of each layer includes multiple path points to be printed, the tangent direction of the surface at each path point is the printing direction of the path point, and the coordinates of each path point are three-dimensional coordinates in the coordinate system of the object to be printed; The angle at which the end of the 6-axis 3D printer's robotic arm rotates around the Z axis of the reference coordinate system when printing each path point of each layer. as a variable to be optimized, and determining an expression of the variable to be optimized according to the coordinates of each path point in the printing path of each layer; Determine the inverse kinematics model of the manipulator of the 6-axis 3D printer and solve the inverse kinematics model of the manipulator to obtain the rotation angle of each axis of the 6-axis 3D printer and the angle The angular relationship between Determining an optimization objective function based on the angle relationship and the expression of the variable to be optimized, and setting a robot arm axis limit constraint condition and a robot arm singular point constraint condition for the optimization objective function; Based on the optimization objective function, the robot arm axis limit constraint condition, the robot arm singular point constraint condition and the angle relationship, the optimized rotation angle of each axis of the 6-axis 3D printer when printing each path point of each layer is determined.

2. The layer-by-layer joint trajectory optimization method for 6-axis 3D printing according to claim 1, characterized in that: The step of determining the optimized rotation angle of each axis of the 6-axis 3D printer when printing each path point of each layer based on the optimization objective function, the robot arm axis limit constraint, the robot arm singular point constraint, and the angle relationship comprises: Based on the robot axis limit constraint condition and the robot singular point constraint condition, the optimization objective function is solved to obtain the optimized angle when printing each path point of each layer. ; According to the optimized angle The optimized rotation angle of each axis of the 6-axis 3D printer when printing each path point of each layer is obtained based on the angle relationship.

3. The layer-by-layer joint trajectory optimization method for 6-axis 3D printing according to claim 1, characterized in that: The expression of the variable to be optimized is as follows: ； ； in, is the variable to be optimized, Indicates printing Layer The angle at which the end of the robotic arm of the 6-axis 3D printer rotates around the Z axis of the reference coordinate system when there are path points , , , represents the total number of layers, Indicates the The total number of path points contained in the layer's printing path. is the default value, and represents the order, For the said Layer The y coordinate value of each path point, For the said Layer The x-coordinate value of each path point, , represents the matrix of coefficients to be optimized, Each element in is a coefficient to be optimized.

4. The layer-by-layer joint trajectory optimization method for 6-axis 3D printing according to claim 1, characterized in that: The robot arm axis limit constraint condition is used to limit the rotation angle of each axis of the 6-axis 3D printer to not exceed a preset limit angle, and the robot arm singular point constraint condition is used to prevent the robot arm movement of the 6-axis 3D printer from having singular points during the printing process. The expressions of the optimization objective function, the robot arm axis limit constraint condition, and the robot arm singular point constraint condition are respectively as follows: ； ； ； in, represents the optimization objective function, Indicates the limit constraint condition of the manipulator axis, represents the singular point constraint condition of the manipulator, Indicates the The total number of path points contained in the layer's printing path. , represents the total number of layers, Indicates the first Axles, , Indicates the The weighted values ​​of the axes, Indicates that when printing the Layer The first path point of the 6-axis 3D printer The rotation angle of each axis, Indicates the The average angle of the axes, , For the said The maximum rotation angle of each axis, For the said The minimum rotation angle of each axis, For the said The stroke of each axis, , , , express The minimum value in express The maximum value in Representation matrix The eigenvalues ​​of represents the Jacobian matrix of the robotic arm of the 6-axis 3D printer, is the default value.

5. The layer-by-layer joint trajectory optimization method for 6-axis 3D printing according to claim 1, characterized in that: The rotation angle of each axis of the 6-axis 3D printer is The expression for the angle relationship between them is as follows: ； ； ； ； ； ； ； ； ； ； ； in, represent , represent , the rest are similar; express , express , the rest are similar; represents the distance between Z2 and Z3, represents the distance between Z3 and Z4, represents the distance between X3 and X2, Represents the distance between X4 and X3, where Z2 refers to the Z axis of the second joint coordinate system, and X2 refers to the X axis of the second joint coordinate system, and the rest are similar.

6. The layer-by-layer joint trajectory optimization method for 6-axis 3D printing according to claim 1, characterized in that: The angle at which the end of the 6-axis 3D printer's robotic arm rotates around the X-axis of the reference coordinate system when printing each path point of each layer , the angle of rotation around the Y axis of the reference coordinate system The angles mentioned above are used To express; The angle The expression is as follows: ； ； ； The angle The expression is as follows: ； ； ； in, 、 and Respectively represent the X, Y, and Z components of the printing direction of each path point of each layer in the robot end coordinate system.

7. The layer-by-layer joint trajectory optimization method for 6-axis 3D printing according to claim 1, characterized in that: The position of the end-arm of the 6-axis 3D printer when printing each path point of each layer The position and posture are determined by the coordinates of the print head of the 6-axis 3D printer in the robot base coordinate system and the coordinates of the path point. The expression is as follows: ； ； ； ； in, 、 and represents the coordinates of the print head in the robot base coordinate system, 、 and Indicates the Layer The coordinates of the path points, , , represents the total number of layers, Indicates the The total number of path points contained in the layer's print path.

8. The layer-by-layer joint trajectory optimization method for 6-axis 3D printing according to claim 1, characterized in that: When the object to be printed is a thin-walled rotating body, the step of obtaining the total number of layers required to be printed and the printing path of each layer when printing the object layer by layer includes: Determining a geometric model of the thin-walled body of revolution; Slicing the geometric model in a horizontal direction to divide the geometric model into a plurality of horizontal layers, and obtaining a total number of layers required for printing the thin-walled rotational body layer by layer; Each horizontal layer is sliced ​​longitudinally to determine the path points that need to be printed when printing each horizontal layer and the three-dimensional coordinates of each path point in the coordinate system of the object to be printed, wherein all the path points that need to be printed when printing a horizontal layer constitute the printing path of the horizontal layer.

9. The layer-by-layer joint trajectory optimization method for 6-axis 3D printing according to claim 8, characterized in that: The busbars of the plurality of horizontal layers have the same length, and the The central angle of the layer is , , is the busbar length for each horizontal layer, is the radius of the thin-walled body of revolution, , Indicates the total number of layers.

10. A 6-axis 3D printing layer-by-layer joint trajectory optimization device, comprising a processor, a communication interface, a memory, and a communication bus, characterized in that: The processor, the communication interface and the memory communicate with each other via the communication bus; The memory is used to store computer programs; The processor is used to implement the steps of the layer-by-layer joint trajectory optimization method for 6-axis 3D printing described in any one of claims 1-9 when executing the program stored in the memory.

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