Method and apparatus for robot joint angle generation, and robot system

Abstract

A method and apparatus for robot joint angle generation, and a robot system. The method for robot joint angle generation comprises: acquiring, in a standard form, a DH parameter set of a robot requiring a solution, a base coordinate system transformation matrix between the robot requiring a solution and a standard robot, and a joint angle transformation relationship between the robot requiring a solution and the standard robot; on the basis of the base coordinate system transformation matrix, converting an end pose of the robot requiring a solution into a standard end pose; on the basis of the DH parameter set in the standard form of the robot requiring a solution and the standard end pose, performing an inverse kinematics calculation to obtain, in a standard form, a joint angle of the robot requiring a solution; and, on the basis of the joint angle transformation relationship between the robot requiring a solution and the standard robot and the joint angle in the standard form of the robot requiring a solution, obtaining the actual joint angle of the robot requiring a solution.

Description

Method and device for generating joint angles of robot and robot system Technical Field

[0001] The present disclosure relates to the technical field of industrial robots, and in particular to a method, device, electronic device, readable storage medium, and robot system for generating joint angles of a robot. Background Art

[0002] In the field of robotic applications, kinematics is the key foundation for various applications. Calculations of inverse kinematics are usually performed using analytical and numerical methods. Numerical solutions usually use numerical iteration methods to calculate inverse kinematics problems, and their convergence and computational efficiency are the main issues. Analytical solutions have high computational efficiency and can select inverse solutions based on the robot's configuration, making them the first choice for robotic applications. Analytical solutions to robot kinematics are usually calculated using traditional methods such as analytical and geometric methods, which rely on the establishment of a mathematical model of the robot. The DH parameter model is applicable to robots of any configuration and is usually used to establish a mathematical model of the robot. Therefore, most robot kinematic calculations rely on the DH parameter model.

[0003] Robot inverse kinematics is a fundamental problem in robotics, which involves calculating the joint angles of a robot to achieve the desired end-effector position and orientation. Analytical methods for robot inverse kinematics problems are more popular than numerical methods because they provide closed-form equations that can be solved efficiently and accurately. However, deriving analytical solutions to inverse kinematics problems for robots with arbitrary kinematic structures is challenging, but the calculation method for the analytical solutions is the same when the robot configuration is consistent. Since DH parameter modeling can be applied to robots of any configuration, most analytical solutions rely on the DH parameter model. The establishment of the DH parameter model depends on the position of the robot's base coordinate system and flange coordinate system (end coordinate system), as well as the rotation direction of the joints. When the robot configuration is consistent, the final DH model established is inconsistent due to the different positions of the base coordinate system, flange coordinate system and joint rotation direction of different robot manufacturers, which limits the versatility of the analytical solution.

[0004] In practical applications, a general calculation method for inverse kinematics analytical solutions is needed.

[0005] Summary of the Invention

[0006] The present disclosure provides a method, device, electronic device, readable storage medium and robot system for generating joint angles of a robot.

[0007] According to one aspect of the present disclosure, a method for generating joint angles of a robot is provided, comprising: obtaining a standard form DH parameter set of the robot to be solved, a base coordinate system transformation matrix between the robot to be solved and the standard robot, and a joint angle transformation relationship between the robot to be solved and the standard robot based on the initial DH parameter set of the robot to be solved and the standard form DH parameter set of a standard robot; converting the end pose of the robot to be solved into a standard end pose based on the base coordinate system transformation matrix; performing inverse kinematics calculation based on the standard form DH parameter set of the robot to be solved and the standard end pose to obtain the standard form joint angles of the robot to be solved; and obtaining the actual joint angles of the robot to be solved based on the joint angle transformation relationship between the robot to be solved and the standard robot and the standard form joint angles of the robot to be solved.

[0008] According to the joint angle generation method for a robot of at least one embodiment of the present disclosure, the robot to be solved and the standard robot are robots with the same configuration; the number of the joint angles is one or more than two.

[0009] According to the joint angle generation method for a robot of at least one embodiment of the present disclosure, the kinematic model of the robot to be solved including the initial DH parameter set and the kinematic model of the standard robot including the standard form DH parameter set are established based on the same modeling method.

[0010] According to at least one embodiment of the present disclosure, a method for generating joint angles for a robot includes: obtaining each joint axis of the robot, taking the central axis of each joint axis as the Z-axis direction, and determining the positive direction of the Z-axis based on the right-hand rule and the joint rotation direction;

[0011] Obtain the common perpendicular line between the central axis of the i-th joint axis and the central axis of the i+1-th joint axis or the intersection of the central axis of the i-th joint axis and the central axis of the i+1-th joint axis to obtain the origin of the i-th joint coordinate system, where i is a natural number greater than or equal to 1; set the X-axis direction to be along the direction of the common perpendicular line. If the central axis of the i-th joint axis and the central axis of the i+1-th joint axis intersect, set the X-axis direction to be perpendicular to the common plane where the central axis of the i-th joint axis and the central axis of the i+1-th joint axis are located; and determine the Y-axis direction based on the Z-axis direction, the X-axis direction and the right-hand rule to complete the establishment of the i-th joint coordinate system.

[0012] According to the joint angle generation method for a robot of at least one embodiment of the present disclosure, the modeling method further includes establishing a base coordinate system and an end coordinate system of each robot based on a robot manual of each robot.

[0013] According to the joint angle generation method for a robot of at least one embodiment of the present disclosure, the modeling method is constrained based on the following modeling rules: the origin of the i-th joint coordinate system of each robot with the same configuration is located at the intersection of the common perpendicular line of the central axis of the i-th joint axis, the central axis of the i+1-th joint axis and the central axis of the i-th joint axis; the Z axis of the 1st joint coordinate system of each robot with the same configuration and the Z axis of the base coordinate system are collinear and both point upward; the translation distance of two adjacent overlapping joints or two parallel joints of each robot with the same configuration along the Z axis of the i-th joint coordinate system can be moved or merged; and the absolute value of the translation distance of the current joint coordinate system of each robot with the same configuration along the X axis of the previous joint coordinate system is the same.

[0014] According to at least one embodiment of the present disclosure, a method for generating joint angles for a robot is provided. The kinematic model including the initial DH parameter set and the kinematic model including the standard form DH parameter set are both constructed based on the inter-coordinate transformation relationship between two adjacent coordinate systems of the robot. The DH parameters are expressed as four transformation matrices:

[0015] ; Among them, the rotation angle around the X axis of the previous coordinate system is α i-1 , the translation distance along the X axis of the previous coordinate system is a i-1 , the rotation angle around the Z axis of the current coordinate system is θ i , the translation distance along the Z axis of the current coordinate system is d i , i is a natural number greater than or equal to 1; the transformation relationship between the coordinate systems is expressed by the transformation relationship matrix between the coordinate systems, which is constructed as a homogeneous transformation matrix:

[0016] According to the joint angle generation method for a robot according to at least one embodiment of the present disclosure, the kinematic model of the robot is represented as the product of the transformation relationship matrices between all coordinate systems:

[0017] According to at least one embodiment of the present disclosure, a joint angle generation method for a robot is disclosed. Based on the initial DH parameter set of the robot to be solved and the standard form DH parameter set of the standard robot, the standard form DH parameter set of the robot to be solved, the base coordinate system transformation matrix between the robot to be solved and the standard robot, and the joint angle transformation relationship between the robot to be solved and the standard robot are obtained, including: constructing a model conversion equation based on the product of all coordinate system transformation relationship matrices of the kinematic model of the robot to be solved and the product of all coordinate system transformation relationship matrices of the kinematic model of the standard robot; in the model conversion equation, the DH parameters of each coordinate system transformation relationship matrix of the robot to be solved and the each coordinate system transformation relationship matrix of the standard robot are correspondingly compared to obtain the DH parameter difference between each coordinate system of the robot to be solved and each corresponding coordinate system of the standard robot, so as to obtain the standard form DH parameter set of the robot to be solved; and obtaining the base coordinate system transformation matrix based on the DH parameter difference between the first joint axis of the standard robot and the first joint axis of the robot to be solved; obtaining the joint angle transformation relationship based on the corresponding DH parameter difference between all joint axes of the standard robot and all joint axes of the robot to be solved.

[0018] According to at least one embodiment of the present disclosure, a joint angle generation method for a robot is provided, based on the corresponding DH parameter differences between all joint axes of a standard robot and all joint axes of a robot to be solved, and includes: recursively obtaining the DH parameter differences between each subsequent joint axis of the standard robot and each subsequent joint axis of the robot to be solved based on the obtained DH parameter difference between the first joint axis of the standard robot and the first joint axis of the robot to be solved.

[0019] According to another aspect of the present disclosure, a joint angle generation device for a robot is provided, comprising: a DH parameter transformation module, which obtains the standard form DH parameter set of the robot to be solved, the base coordinate system transformation matrix between the robot to be solved and the standard robot, and the joint angle transformation relationship between the robot to be solved and the standard robot based on the initial DH parameter set of the robot to be solved and the standard form DH parameter set of the standard robot; a standard end pose acquisition module, which converts the end pose of the robot to be solved into the standard end pose based on the base coordinate system transformation matrix; an analytical solution solving module, which performs inverse kinematics calculation based on the standard form DH parameter set of the robot to be solved and the standard end pose to obtain the standard form joint angle of the robot to be solved; and a joint angle transformation module, which obtains the actual joint angle of the robot to be solved based on the joint angle transformation relationship between the robot to be solved and the standard robot and the standard form joint angle of the robot to be solved.

[0020] According to another aspect of the present disclosure, an electronic device is provided, comprising: a memory storing execution instructions; and a processor executing the execution instructions stored in the memory, so that the processor executes the joint angle generation method for a robot according to any embodiment of the present disclosure.

[0021] According to another aspect of the present disclosure, a readable storage medium is provided, wherein the readable storage medium stores execution instructions, and when the execution instructions are executed by a processor, the method for generating joint angles for a robot according to any embodiment of the present disclosure is used.

[0022] According to another aspect of the present disclosure, a robot system is provided, comprising: a robot, wherein the robot is a multi-joint robotic arm, the robot having a base and an end, the robot being capable of being set on a workbench or on the ground based on the base, and the end being used to connect an actuator; and a readable storage medium according to any embodiment of the present disclosure, wherein the robot performs inverse kinematics solution based on execution instructions stored in the readable storage medium.

[0023] According to the robot system of at least one embodiment of the present disclosure, the end is a flange.

[0024] According to the robot system of at least one embodiment of the present disclosure, the actuator includes a manipulator capable of grasping. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings illustrate exemplary embodiments of the present disclosure and together with the description serve to explain the principles of the present disclosure. These drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification.

[0026] FIG1 is a schematic diagram of the modified DH parameters disclosed in the present invention.

[0027] FIG2 is a flow chart of a method for generating joint angles of a robot according to an embodiment of the present disclosure.

[0028] FIG3 is a schematic diagram of a process for establishing a robot joint coordinate system in a modeling method according to an embodiment of the present disclosure.

[0029] FIG4 shows the model structure of the industrial robot Fanuc LR Mate 200iD.

[0030] Figure 5 is a flowchart of obtaining the standard form of DH parameter set of the robot to be solved, the base coordinate system transformation matrix between the robot to be solved and the standard robot, and the joint angle transformation relationship between the robot to be solved and the standard robot in one embodiment of the present disclosure.

[0031] FIG6 is a schematic diagram of random sampling points of joint angles generated by the joint space according to an embodiment of the present disclosure.

[0032] FIG7 is a schematic block diagram of the structure of a joint angle generating device implemented in hardware using a processing system according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0033] The present disclosure will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the relevant content and are not intended to limit the present disclosure. It should also be noted that, for ease of description, only the portions relevant to the present disclosure are shown in the accompanying drawings.

[0034] Explanation of terms:

[0035] DH parameter model: In 1955, Jacques Denavit and Richard Hartenberg first introduced the Denavit-Hartenberg parameters, and the DH parameters became a widely used method for representing robot kinematics. The DH parameters are a set of parameters that describe the transformation relationship between two coordinate systems to standardize the coordinate system of the spatial link. The present disclosure is preferably modeled with improved DH parameters. As shown in Figure 1, the improved DH parameters of the present disclosure describe the transformation matrix between two adjacent coordinate systems through four parameters, namely: the rotation angle αi-1 of the Z axis of the previous coordinate system relative to the Z axis of the current coordinate system around the X axis of the previous coordinate system, the translation distance ai-1 of the Z axis of the previous coordinate system relative to the Z axis of the current coordinate system along the X axis of the previous coordinate system, the rotation angle θi of the X axis of the previous coordinate system relative to the X axis of the current coordinate system around the Z axis of the current coordinate system, and the translation distance di of the X axis of the previous coordinate system relative to the X axis of the current coordinate system along the Z axis of the current coordinate system.

[0036] The following describes in detail the method and device for generating joint angles of a robot disclosed in the present invention in conjunction with FIG. 1 to FIG. 7 .

[0037] FIG2 is a flow chart of a method for generating joint angles of a robot according to an embodiment of the present disclosure.

[0038] 2 , in some embodiments of the present disclosure, a method S100 for generating joint angles for a robot according to the present disclosure includes:

[0039] S102, based on the initial DH parameter set of any one robot to be solved among the multiple robots having the same configuration and the standard form DH parameter set of the standard robot among the multiple robots, obtain the standard form DH parameter set of the robot to be solved, the base coordinate system transformation matrix between the robot to be solved and the standard robot ( StdBase T Base ) and the joint angle transformation relationship between the robot to be solved and the standard robot; wherein the DH parameter set can be a DH parameter list.

[0040] S104, based on the base coordinate system transformation matrix ( StdBase T Base ) The end position of the robot to be solved ( Base T e ) is converted to the standard form of the end pose ( StdBase T e ); wherein the end position can be a flange position.

[0041] S106, based on the standard form of the robot to be solved DH parameter set and the standard end position ( StdBase T e) performs inverse kinematics calculations to obtain the standard form of joint angles (JointAngles) of the robot to be solved.

[0042] S108 , obtaining the actual joint angles of the robot to be solved based on the joint angle transformation relationship between the robot to be solved and the standard robot and the joint angles of the standard form of the robot to be solved.

[0043] In the joint angle generation method for a robot disclosed in the present invention, the robot to be solved and the standard robot are robots with the same configuration, and the number of joint angles of the robot is one or more than two.

[0044] The differences between robots of the same configuration but different brands primarily exist in the base coordinate system, joint rotation direction, zero point position, flange coordinate system, and connecting rod length. The base and flange coordinate systems can be considered fixed transformations, while joint angles may differ in direction and zero point. Connecting rod length does not affect kinematic calculations.

[0045] Therefore, the present disclosure takes calculating the fixed poses of the base coordinate system and the flange coordinate system and determining the differences in joint angles of the DH models of different robots as the ultimate goal of converting between the DH models of different robots.

[0046] The joint angle generation method for a robot disclosed in the present invention first takes one of multiple robots with the same configuration as the standard robot, and takes the DH parameter set of the standard robot as the standard DH parameter set, and converts the initial DH parameter set of the robot to be solved (that is, any robot other than the standard robot among the above-mentioned multiple robots) into a standard DH parameter set, so that there is no need to re-model the robot with the same configuration as the standard robot (the robot to be solved described above).

[0047] In some embodiments of the present disclosure, the present disclosure compares the DH parameter set of the robot to be solved with the DH parameter set of a standard robot to obtain the DH parameter difference between the two, thereby converting the initial DH parameter set of the robot to be solved into a standard DH parameter set.

[0048] In some preferred embodiments of the present disclosure, the initial DH parameter set of the robot to be solved is transformed based on the DH parameter difference between the two obtained above to obtain a standard form of DH parameter set of the robot to be solved.

[0049] Furthermore, the present disclosure converts the end pose of the robot to be solved into a standard end pose (i.e., a standard form end pose) based on the base coordinate system transformation matrix between the robot to be solved and the standard robot, and obtains the standard form joint angles of the robot to be solved based on the standard end pose of the robot to be solved and the standard form DH parameter set. There is no need to re-model the robot to be solved separately, but the standard form joint angles are obtained with the help of the standard form DH parameter set of the robot to be solved.

[0050] Furthermore, the actual joint angles of the robot to be solved are obtained based on the joint angle transformation relationship described above and the standard form of the joint angles of the robot to be solved, thereby completing the generation of the joint angles of the robot to be solved.

[0051] The joint angle generation method disclosed in the present invention does not need to re-model each robot to be solved separately during the entire process of performing inverse kinematics solution on the robot to be solved to obtain its joint angle based on its end posture, which greatly simplifies the inverse kinematics solution process of each robot to be solved and saves computing power.

[0052] The base coordinate systems of the robot to be solved and the standard robot described above may be the base coordinate systems of the robots (eg, the base coordinate system of the robotic arm).

[0053] In some embodiments of the present disclosure, the joint angle transformation relationship between the robot to be solved and the standard robot is obtained based on the DH parameter difference described above.

[0054] It should be noted that in the joint angle generation method for a robot disclosed in the present invention, the DH parameter-based kinematic model (DH parameter model) of the robot to be solved described above and the DH parameter-based kinematic model (DH parameter model) of the standard robot are established based on the same modeling method, so that the initial DH parameter set of the robot to be solved can be more easily converted into a standard DH parameter set.

[0055] FIG3 is a schematic diagram of a process for establishing a robot joint coordinate system in a modeling method according to an embodiment of the present disclosure.

[0056] 3 , in some embodiments of the present disclosure, the modeling method S200 of the present disclosure includes:

[0057] S202 , obtaining each joint axis of the robot, taking the central axis of each joint axis as the Z-axis direction, and determining the positive direction of the Z-axis based on the right-hand rule and the joint rotation direction.

[0058] S204. Obtain the common perpendicular line between the central axis of the i-th joint axis and the central axis of the (i+1)-th joint axis or the intersection of the central axis of the i-th joint axis and the central axis of the (i+1)-th joint axis to obtain the origin of the i-th joint coordinate system, where i is a natural number greater than or equal to 1.

[0059] S206. Set the X-axis direction to be along the common vertical line. If the central axis of the i-th joint axis and the central axis of the (i+1)-th joint axis intersect, set the X-axis direction to be perpendicular to the common plane where the central axis of the i-th joint axis and the central axis of the (i+1)-th joint axis are located.

[0060] S208. Determine the Y-axis direction based on the Z-axis direction, the X-axis direction and the right-hand rule, and complete the establishment of the i-th joint coordinate system.

[0061] In some embodiments of the present disclosure, the modeling method of the present disclosure further includes establishing a base coordinate system and an end coordinate system (flange coordinate system) of each robot based on the robot manual of each robot, so as to make as many parameters as possible zero.

[0062] In this disclosure, for robots of the same configuration, a DH parameter model of one robot is selected as the standard parameter model. Taking the common configuration of industrial robots (where axes 1 and 2 are perpendicular, axes 2 and 3 are parallel, axes 3 and 4 are perpendicular, and the centerlines of axes 4, 5, and 6 intersect at a point) as an example, a DH parameter model, i.e., a kinematic model based on DH parameters, is established according to the improved DH parameter establishment rules disclosed in this disclosure (described below) and the base coordinate system position, flange coordinate system position, and joint rotation directions specified in the robot manual. The method disclosed in this disclosure is also applicable to other configurations of industrial robots.

[0063] In a preferred embodiment of the present disclosure, the kinematic model based on DH parameters of the present disclosure is constructed based on the coordinate transformation relationship between two adjacent coordinate systems of the robot (including the joint coordinate system, the base coordinate system, and the end coordinate system), wherein the DH parameters are expressed as four transformation matrices (the DH parameters of the robot to be solved and the DH parameters of the standard robot are both expressed in this way):

[0064] The rotation angle around the X-axis of the previous coordinate system is αi-1, the translation distance along the X-axis of the previous coordinate system is ai-1, the rotation angle around the Z-axis of the current coordinate system is θi, the translation distance along the Z-axis of the current coordinate system is di, and i is a natural number greater than or equal to 1.

[0065] The transformation relationship between coordinate systems is expressed as a matrix of transformation relationship between coordinate systems, which is constructed as a homogeneous transformation matrix:

[0066] In a preferred embodiment of the present disclosure, the kinematic model of the robot of the present disclosure based on DH parameters is expressed as the product of the transformation relationship matrices between all coordinate systems:

[0067] In order to illustrate the effectiveness of the modeling method of the present disclosure, the present disclosure selects five example robots, and the DH parameter models established based on the modeling method of the present disclosure are shown in Table 1.

[0068] Table 1: Example of robot DH parameter model (before conversion)

[0069] Exemplarily, the present disclosure uses the DH parameter model of the industrial robot Fanuc LR Mate 200iD as a standard form of DH parameter model, and takes the industrial robot Fanuc LR Mate 200iD as an example (Figure 4 shows the model structure of the industrial robot Fanuc LR Mate 200iD). According to the Piper criterion, it can be determined that this configuration can obtain a closed solution through analytical methods, and there can be up to 8 sets of solutions. The ultimate goal of inverse kinematics is to obtain the mapping relationship between the robot's end posture and joint angles. There are many ways to solve the inverse kinematics analytical solution. A method similar to the OPW solver can be used to solve the end position and posture separately. The first three axes are solved through geometric relationships, and the last three axes are calculated through matrix element correspondence. Alternatively, all joint angles can be calculated through matrix correspondence. Exemplarily, the robot's kinematic model is expressed as a transformation matrix of the end (EE, End-Effector) coordinate system relative to the base (B, Base) coordinate system. B T ee and joint angle θ i , the relationship between i∈[0,n] is modeled through the joint coordinate system, and the end pose is composed of the multiplication of each joint coordinate system: B T ee = B T1 1 T2 2 T3 3 T4 4 T5 5 T6 6 T7

[0070] Multiply both sides of the above equation by [ B T1] -1 ,get: [ B T1] -1 . B T ee = 1 T2 2 T3 3 T4 4T5 5 T6 6 T7

[0071] Then, by making some corresponding elements in the two matrices equal, we can solve for θ1, and then substitute θ1 into the above equation and multiply both ends of the equation by [ 1 T2] -1 get: [ 1 T2] -1 ·[ B T1] -1 · B T ee = 2 T3 3 T4 4 T5 5 T6 6 T7

[0072] Then, by making some corresponding elements in the two matrices equal, we can solve for θ3. By doing this in sequence, we can get all the joint angles θ i , i∈[0,n]. The inverse kinematics solution itself is not the focus of this disclosure and is not specifically limited in this disclosure. A commonly used analytical solution method can be used to calculate the analytical solution of inverse kinematics based on a standard parameter model, and finally encapsulated into a function, as exemplified by the following formula:

[0073] (0 1，i , 0 2，i ,θ 3，i ,θ 4，i ,θ 5，i ,θ 6，i )i∈[1,8]=getInverseKinematics( 0 T e , DHList)

[0074] The input is the position of the robot's end (such as the flange) relative to the base (base coordinate system) and the DH parameter list (DHList), and the output is 8 sets of joint angles (a six-degree-of-freedom robot needs to output 8 sets of joint angles).

[0075] By converting the DH parameter model of different robots with the same configuration, that is, the initial DH parameter model, into a standard form of DH parameter model, the analytical solution function of the standard configuration can be used to finally realize the generation of actual joint angles of each robot with the same configuration as the standard robot.

[0076] In order to efficiently and accurately convert the initial DH parameter model of the robot to be solved into a standard DH parameter model, the modeling method based on the improved DH parameters disclosed in the present invention is constrained based on the following modeling rules:

[0077] (1) The origin of the i-th joint coordinate system of each robot with the same configuration is located at the intersection of the central axis of the i-th joint axis and the common perpendicular line of the central axis of the i+1-th joint axis and the central axis of the i-th joint axis.

[0078] (2) The Z axis of the first joint coordinate system and the Z axis of the base coordinate system of each robot with the same configuration are collinear and both point upward.

[0079] (3) The translation distance di along the Z axis of the i-th joint coordinate system of two adjacent overlapping joints or two parallel joints of each robot with the same configuration can be moved or merged.

[0080] (4) The absolute value of the translation distance (ai-1) of the current joint coordinate system (i) of each robot with the same configuration along the X-axis of the previous joint coordinate system (i-1) is the same.

[0081] The improved DH parameter modeling method disclosed in this disclosure, based on the aforementioned modeling rules, ensures that the joint axes of different robots are identical. The differences in joint angles are solely due to differences in rotation direction and zero-point position. Furthermore, the basic rotation transformations are mostly 0, 90, and 180 degrees. Table 2 shows the DH parameters of each robot in Table 1 after transformation to a standard form.

[0082] Table 2: Example of robot DH parameter model (after conversion)

[0083] Here, “direction” means the relationship between the rotation direction of the corresponding joint of the standard robot (same or opposite), and “difference” means the rotation angle deviation of the corresponding joint of the standard robot.

[0084] Taking the Fanuc LR Mate 200iD and Kuka KR 50 R 2500 as examples, the transformation of the two DH parameter models can be obtained by a recursive method (described below). The kinematic models of the two robots based on DH parameters are expressed as:

[0085] 5 , in a preferred embodiment of the present disclosure, in the method for generating joint angles for a robot of the present disclosure, S102, based on an initial DH parameter set of any one robot to be solved among a plurality of robots having the same configuration and a standard form DH parameter set of a standard robot among the plurality of robots, obtains a standard form DH parameter set of the robot to be solved, a base coordinate system transformation matrix between the robot to be solved and the standard robot, and a joint angle transformation relationship between the robot to be solved and the standard robot, including:

[0086] S1022. Construct a model conversion equation based on the product of the transformation relationship matrices between all coordinate systems of the kinematic model (DH parameter model) of the robot to be solved and the product of the transformation relationship matrices between all coordinate systems of the kinematic model (DH parameter model) of the standard robot (so that the two "products" are equal).

[0087] S1024. Perform DH parameter comparisons on the transformation relationship matrices between the coordinate systems of the robot to be solved (Formula (2)) in the model conversion equation and the transformation relationship matrices between the coordinate systems of the standard robot (Formula (2)) to obtain the DH parameter differences between the coordinate systems (base coordinate system, joint coordinate system, end coordinate system) of the robot to be solved and the corresponding coordinate systems of the standard robot, and obtain the standard form of the DH parameter set of the robot to be solved based on the DH parameter differences.

[0088] S1026. Obtain the base coordinate system transformation matrix based on the DH parameter difference between the first joint axis of the standard robot and the first joint axis of the robot to be solved; obtain the joint angle transformation relationship based on the corresponding DH parameter differences between all joint axes of the standard robot and all joint axes of the robot to be solved.

[0089] The purpose of constructing the model conversion equation in step S1022 is to make the total transformation relationship from the end coordinate system of the robot to be solved to the base coordinate system equal to the total transformation relationship from the end coordinate system to the base coordinate system of the standard robot, and then perform DH parameter comparison to obtain DH parameter differences.

[0090] Since the DH parameters disclosed in the present invention are all expressed in the form of transformation matrices (see formula (1) described above), by comparing the DH parameter differences between the transformation relationship matrices between the various coordinate systems of the robot to be solved and the transformation relationship matrices between the various coordinate systems of the standard robot in the model transformation equation, it is possible to obtain the DH parameter differences between the various coordinate systems (base coordinate system, joint coordinate system, terminal coordinate system) of the robot to be solved and the various corresponding coordinate systems (base coordinate system, joint coordinate system, terminal coordinate system) of the standard robot. Based on these DH parameter differences, it is possible to obtain the basic transformation relationship, and it is possible to obtain the basic transformation relationship between the various coordinate systems (base coordinate system, joint coordinate system, terminal coordinate system) of the robot to be solved and the various corresponding coordinate systems (base coordinate system, joint coordinate system, terminal coordinate system) of the standard robot. The basic transformation relationship includes a rotation transformation relationship and / or a translation transformation relationship. For example, the basic transformation relationship between the base coordinate system of the robot to be solved and the base coordinate system of the standard robot can be a Z-axis translation.

[0091] Preferably, the posture of the first joint axis of the present disclosure is expressed in a base coordinate system, the central axis of the first joint axis serves as the Z axis of the base coordinate system, and the first joint coordinate system serves as the base coordinate system.

[0092] Preferably, the corresponding DH parameter differences between all joint axes of the standard robot and all joint axes of the robot to be solved described above include: recursively obtaining the DH parameter differences between each subsequent joint axis of the standard robot and each subsequent joint axis of the robot to be solved based on the obtained DH parameter differences between the first joint axis of the standard robot and the first joint axis of the robot to be solved.

[0093] In some embodiments of the present disclosure, in step S1026, the process of obtaining the base coordinate system transformation matrix and obtaining the joint angle transformation relationship includes:

[0094] (1) The difference in the rotation angle of the Z axis of the currently calculated coordinate system (i-th coordinate system) of the robot to be solved and the standard robot relative to the Z axis of the previous coordinate system around the X axis of the previous coordinate system (i.e., the difference in αi-1, the DH parameter difference) is not transferred to the difference calculation of the next coordinate system to be calculated (i+1-th coordinate system).

[0095] (2) The translation distance difference of the Z axis of the currently calculated coordinate system (i-th coordinate system) of the robot to be solved and the standard robot along the X axis of the previous coordinate system (i.e., the difference of ai-1, i.e., the DH parameter difference) is not transferred to the difference calculation of the next coordinate system to be calculated (i+1-th coordinate system).

[0096] (3) The difference in rotation angle of the X-axis of the currently calculated coordinate system (i-th coordinate system) of the robot to be solved and the standard robot relative to the X-axis of the previous coordinate system around the Z-axis of the current coordinate system (i.e., the difference in θi) is transferred to the difference calculation of the next coordinate system to be calculated (i+1-th coordinate system).

[0097] (4) The translation distance difference (i.e., di) of the X-axis of the currently calculated coordinate system (i-th coordinate system) of the robot to be solved and the standard robot relative to the X-axis of the previous coordinate system along the Z-axis of the current coordinate system is not transferred to the difference calculation of the next coordinate system to be calculated (i+1-th coordinate system).

[0098] Taking Fanuc LR Mate 200iD and Kuka KR 50R 2500 as examples, the model conversion equation in step S1022 is expressed as: 0 T1 1 T2 2 T3 3 T4 4 T5 5 T6 6 T7= 0 T′1· 1 T′2· 2 T′3· 3T′4· 4 T′5· 5 T′6· 6 T′7

[0099] The left side of the equation is the kinematic model of the Fanuc LR Mate 200iD based on DH parameters (i.e., the transformation relationship from the end coordinate system to the base coordinate system), and the right side of the equation is the kinematic model of the Kuka KR 50R 2500 based on DH parameters (i.e., the transformation relationship from the end coordinate system to the base coordinate system).

[0100] First, the relationship between the base coordinate systems of the two DH parameter models can be obtained based on the DH parameters from the first joint coordinate system to the base coordinate system of two industrial robots (Fanuc LR Mate 200iD and Kuka KR 50 R 2500):

[0101] Based on this formula, it can be concluded that the relationship between the base coordinate systems of the two improved DH parameter models is Z-axis translation, the rotation direction of joint 1 is opposite, and the last rotation around the X-axis can be incorporated into the calculation of the next joint.

[0102] Next, calculate the correspondence between joints 2:

[0103] Based on this formula, it can be concluded that the deviation between joint 2 of the two improved DH parameter models is 90°.

[0104] Next, calculate the correspondence between joints 3:

[0105] From this formula, we can conclude that the rotation directions of joint 3 between the two improved DH parameter models are opposite and the deviation is 90°. The same calculation method is used for joints 4, 5, and 6. Joints 4 and 6 rotate in the same direction with no deviation, while joint 5 rotates in the opposite direction with no deviation. In summary, we can use basic transformations to derive the DH parameter list after converting any improved DH parameter model to the standard improved DH parameter model, and obtain the transformation relationship between the base coordinate systems and the relationship between the joint angles.

[0106] In order to verify the accuracy of the inverse kinematics solution method proposed in this disclosure, the inverse kinematics is solved for robots from other manufacturers except Fanuc at any position in the workspace to verify the accuracy of the inverse kinematics. The specific implementation method is: randomly generate a set of joint angles in the joint space, as shown in Figure 6 for random sampling points, and then calculate the forward kinematics to obtain the end position of the robot (the position and spatial angle of the end in the base coordinate system), and then solve the inverse kinematics solution through the joint angle generation method disclosed in this disclosure, and then calculate the forward kinematics of the inverse solution to obtain a set of end position poses, and compare whether the end position pose is within the allowable error range with the given end position pose. Experiments show (see Tables 3 and 4, "Failed" in Table 3 indicates the number of times the inverse kinematics analytical solution failed to be obtained) that the inverse kinematics solution method proposed in this disclosure is not only universal among robots of different brands, but also has high calculation accuracy.

[0107] Table 3: Accuracy comparison results

[0108] Table 4: Computation time comparison results

[0109] The efficiency of inverse kinematics solution is very important. In some upper-level algorithm applications, a large amount of inverse kinematics calculations may be required. In the inverse kinematics solution method disclosed in the present invention (joint angle generation method based on inverse kinematics), the DH parameters of the converted robot only need to be called once for each robot, so the time consumed by the conversion does not need to be considered. The numerical solution of the existing method can only solve one set of solutions each time, and if the conditions are not met, the initial value needs to be re-given and recalculated. The analytical solution of the inverse kinematics solution method disclosed in the present invention can solve multiple sets of solutions each time, and can be selected according to the required constraints. For example, the numerical solution calculation requires 8 calculations to obtain 8 sets of solutions, while the analytical solution of the inverse kinematics solution method disclosed in the present invention only requires 1 calculation.

[0110] It should be noted that the inverse kinematics solution method proposed in the present disclosure is not only applicable to the inverse kinematics calculation of robots with the same configuration, but can also be extended to any calculation based on the DH parameter model, such as dynamics and other applications.

[0111] Based on the above description, the present disclosure further provides a joint angle generating device 1000 for a robot, comprising:

[0112] The DH parameter transformation module 1002 obtains the standard form DH parameter set of the robot to be solved, the base coordinate system transformation matrix between the robot to be solved and the standard robot, and the joint angle transformation relationship between the robot to be solved and the standard robot based on the initial DH parameter set of any one of the multiple robots with the same configuration and the standard form DH parameter set of the standard robot among the multiple robots.

[0113] The standard end-position acquisition module 1004 converts the end-position (flange position) of the robot to be solved into the standard end-position based on the base coordinate system transformation matrix.

[0114] The analytical solution solving module 1006 performs inverse kinematics calculation based on the standard form DH parameter set and the standard end pose of the robot to be solved to obtain the standard form joint angles of the robot to be solved.

[0115] The joint angle transformation module 1008 obtains the actual joint angles of the robot to be solved based on the joint angle transformation relationship between the robot to be solved and the standard robot and the joint angles of the standard form of the robot to be solved.

[0116] The joint angle generating device 1000 for a robot disclosed in the present invention can be implemented in the form of a computer software architecture.

[0117] FIG7 is a schematic block diagram of the structure of a joint angle generating device implemented in hardware using a processing system according to an embodiment of the present disclosure.

[0118] The joint angle generation device 1000 may include corresponding modules for executing each or several steps in the above flowchart. Therefore, each step or several steps in the above flowchart can be executed by the corresponding module, and the device may include one or more of these modules. The module can be one or more hardware modules specifically configured to execute the corresponding steps, or implemented by a processor configured to execute the corresponding steps, or stored in a computer-readable medium for execution by the processor, or implemented by some combination.

[0119] The hardware structure can be implemented using a bus architecture. The bus architecture can include any number of interconnecting buses and bridges, depending on the specific application and overall design constraints of the hardware. Bus 1100 connects various circuits including one or more processors 1200, memory 1300, and / or hardware modules. Bus 1100 can also connect various other circuits 1400 such as peripherals, voltage regulators, power management circuits, external antennas, etc.

[0120] Bus 1100 may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Component Architecture (EISA) bus. Buses can be classified as address buses, data buses, control buses, and the like. For ease of illustration, this figure shows only one connecting line, but this does not imply that there is only one bus or only one type of bus.

[0121] Based on the above description, the present disclosure further provides an electronic device, including: a memory, the memory storing execution instructions; and a processor, the processor executing the execution instructions stored in the memory, so that the processor executes the joint angle generation method for a robot in any embodiment of the present disclosure.

[0122] The present disclosure also provides a readable storage medium, in which execution instructions are stored. When the execution instructions are executed by a processor, they are used to implement the joint angle generation method for a robot according to any embodiment of the present disclosure.

[0123] The present disclosure also provides a robot system, including: a robot, which is a multi-joint robotic arm, the robot having a base and an end, the robot can be set on a workbench or on the ground based on the base, and the end is used to connect an actuator; and a readable storage medium of any embodiment of the present disclosure, the robot performs inverse kinematics solution based on the execution instructions stored in the readable storage medium.

[0124] In some embodiments of the present disclosure, the end of the robot described above in the present disclosure is a flange.

[0125] In some embodiments of the present disclosure, the actuator of the robot described above in the present disclosure includes a manipulator capable of performing a grasping operation.

[0126] It should be noted that any process or method description in the flowcharts of the present disclosure or otherwise described herein can be understood as representing a module, fragment, or portion of code comprising one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present disclosure includes alternative implementations, in which the functions may be performed in a manner not shown or discussed in the order shown, including in a substantially simultaneous manner or in a reverse order depending on the functions involved, as will be understood by those skilled in the art to which the embodiments of the present disclosure pertain. The processor performs the various methods and processes described above. For example, the method embodiments of the present disclosure can be implemented as a software program that is tangibly contained in a machine-readable medium, such as a memory. In some embodiments, part or all of the software program can be loaded and / or installed via a memory and / or a communication interface. When the software program is loaded into the memory and executed by the processor, one or more steps in the method described above can be performed. Alternatively, in other embodiments, the processor can be configured to perform one of the above methods in any other suitable manner (e.g., by means of firmware).

[0127] The logic and / or steps represented in the flowchart or otherwise described herein may be embodied in any readable storage medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device).

[0128] For the purposes of this specification, a "readable storage medium" can be any device that can contain, store, communicate, propagate or transmit a program for use with or in conjunction with an instruction execution system, device or apparatus. More specific examples (a non-exhaustive list) of readable storage media include the following: an electrical connection having one or more wires (electronic device), a portable computer disk cartridge (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and editable read-only memory (EPROM or flash memory), a fiber optic device, and a portable read-only memory (CDROM). In addition, the readable storage medium can even be paper or other suitable medium on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing it in other suitable ways as necessary, and then storing it in a memory.

[0129] Those skilled in the art will understand that all or part of the steps of the above-mentioned implementation method can be accomplished by instructing related hardware through a program, and the program can be stored in a readable storage medium. When the program is executed, it includes one or a combination of the steps of the method implementation method.

[0130] Furthermore, the functional units in the various embodiments of the present disclosure may be integrated into a single processing module, each unit may exist physically separately, or two or more units may be integrated into a single module. The aforementioned integrated modules may be implemented in the form of hardware or software functional modules. If the integrated modules are implemented as software functional modules and sold or used as independent products, they may also be stored in a readable storage medium. The storage medium may be a read-only memory, a magnetic disk, or an optical disk, etc.

[0131] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0132] Those skilled in the art will appreciate that the above embodiments are merely intended to clearly illustrate the present disclosure and are not intended to limit the scope of the present disclosure. Other changes or modifications may be made based on the above disclosure, and such changes or modifications are still within the scope of the present disclosure.

Claims

1. A method for generating joint angles of a robot, characterized in that: include: Based on the initial DH parameter set of the robot to be solved and the standard form DH parameter set of the standard robot, the standard form DH parameter set of the robot to be solved, the base coordinate system transformation matrix between the robot to be solved and the standard robot, and the joint angle transformation relationship between the robot to be solved and the standard robot are obtained; Based on the base coordinate system transformation matrix, the end position of the robot to be solved is converted into a standard end position; Performing inverse kinematics calculation based on the standard form DH parameter set of the robot to be solved and the standard end position to obtain the standard form joint angles of the robot to be solved; and The actual joint angles of the robot to be solved are obtained based on the joint angle transformation relationship between the robot to be solved and the standard robot and the joint angles of the standard form of the robot to be solved.

2. The method for generating joint angles of a robot according to claim 1, characterized in that: The robot to be solved and the standard robot are robots with the same configuration; the number of the joint angles is one or more than two.

3. The method for generating joint angles for a robot according to claim 1, characterized in that: The kinematic model of the robot to be solved including the initial DH parameter set and the kinematic model of the standard robot including the DH parameter set in a standard form are established based on the same modeling method.

4. The method for generating joint angles for a robot according to claim 3, characterized in that: The modeling method comprises: Get each joint axis of the robot, take the central axis of each joint axis as the Z-axis direction, and determine the positive direction of the Z-axis based on the right-hand rule and the joint rotation direction; Obtain the common perpendicular line between the central axis of the i-th joint axis and the central axis of the i+1-th joint axis or the intersection of the central axis of the i-th joint axis and the central axis of the i+1-th joint axis to obtain the origin of the i-th joint coordinate system, where i is a natural number greater than or equal to 1; The X-axis direction is set to be along the direction of the common perpendicular line. If the central axis of the i-th joint axis intersects the central axis of the i+1-th joint axis, the X-axis direction is set to be perpendicular to the common plane where the central axis of the i-th joint axis and the central axis of the i+1-th joint axis are located; and Based on the Z-axis direction, the X-axis direction and the right-hand rule, the Y-axis direction is determined to complete the establishment of the i-th joint coordinate system.

5. The method for generating joint angles for a robot according to claim 4, characterized in that: The modeling method further includes establishing a base coordinate system and an end coordinate system of each robot based on a robot manual of each robot.

6. The method for generating joint angles for a robot according to claim 4, characterized in that: The modeling approach is constrained based on the following modeling rules: The origin of the i-th joint coordinate system of each robot with the same configuration is located at the intersection of the central axis of the i-th joint axis and the common perpendicular line of the central axis of the i+1-th joint axis and the central axis of the i-th joint axis; The Z axis of the first joint coordinate system of each robot with the same configuration is collinear with the Z axis of the base coordinate system and both point upward; The two adjacent overlapping joints or two parallel joints of each robot with the same configuration are The Z-axis translation distance of the joint coordinate system can be moved or merged; and The absolute value of the translation distance of the current joint coordinate system of each robot with the same configuration along the X-axis of the previous joint coordinate system is the same.

7. The method for generating joint angles for a robot according to claim 3, characterized in that: The kinematic model including the initial DH parameter set and the kinematic model including the standard form DH parameter set are both constructed based on the coordinate transformation relationship between two adjacent coordinate systems of the robot, wherein the DH parameters are expressed as four transformation matrices: Among them, the rotation angle around the X axis of the previous coordinate system is α i-1 , the translation distance along the X axis of the previous coordinate system is a i-1 , the rotation angle around the Z axis of the current coordinate system is θ i , the translation distance along the Z axis of the current coordinate system is d i , i is a natural number greater than or equal to 1; The transformation relationship between the coordinate systems is expressed by the transformation relationship matrix between the coordinate systems, which is constructed as a homogeneous transformation matrix:

8. The method for generating joint angles for a robot according to claim 7, characterized in that: The kinematic model of the robot is expressed as the product of the transformation matrices between all coordinate systems:

9. The method for generating joint angles for a robot according to claim 8, characterized in that: Based on the initial DH parameter set of the robot to be solved and the standard form DH parameter set of the standard robot, the standard form DH parameter set of the robot to be solved, the base coordinate system transformation matrix between the robot to be solved and the standard robot, and the joint angle transformation relationship between the robot to be solved and the standard robot are obtained, including: A model conversion equation is constructed based on the product of the transformation relationship matrices between all coordinate systems of the kinematic model of the robot to be solved and the product of the transformation relationship matrices between all coordinate systems of the kinematic model of the standard robot; Comparing the transformation relationship matrices between the coordinate systems of the robot to be solved and the transformation relationship matrices between the coordinate systems of the standard robot in the model conversion equation accordingly, obtaining the DH parameter differences between the coordinate systems of the robot to be solved and the corresponding coordinate systems of the standard robot, so as to obtain the DH parameter set of the standard form of the robot to be solved; and The base coordinate system transformation matrix is ​​obtained based on the DH parameter difference between the first joint axis of the standard robot and the first joint axis of the robot to be solved; the joint angle transformation relationship is obtained based on the corresponding DH parameter differences between all joint axes of the standard robot and all joint axes of the robot to be solved.

10. The method for generating joint angles for a robot according to claim 9, characterized in that: Based on the corresponding DH parameter differences between all joint axes of the standard robot and all joint axes of the robot to be solved, including: Based on the obtained DH parameter difference between the first joint axis of the standard robot and the first joint axis of the robot to be solved, the DH parameter difference between each subsequent joint axis of the standard robot and each subsequent joint axis of the robot to be solved is recursively obtained.

11. A joint angle generating device for a robot, characterized in that: include: A DH parameter transformation module, wherein the DH parameter transformation module obtains a standard form DH parameter set of the robot to be solved, a base coordinate system transformation matrix between the robot to be solved and the standard robot, and a joint angle transformation relationship between the robot to be solved and the standard robot based on an initial DH parameter set of the robot to be solved and a standard form DH parameter set of a standard robot; A standard terminal posture acquisition module, wherein the standard terminal posture acquisition module converts the terminal posture of the robot to be solved into a standard terminal posture based on the base coordinate system transformation matrix; An analytical solution solving module, wherein the analytical solution solving module performs inverse kinematics calculation based on the standard form DH parameter set of the robot to be solved and the standard end position to obtain the standard form joint angles of the robot to be solved; as well as A joint angle transformation module is provided, wherein the joint angle transformation module obtains the actual joint angle of the robot to be solved based on the joint angle transformation relationship between the robot to be solved and the standard robot and the joint angle of the standard form of the robot to be solved.

12. A robot system, characterized in that: include: A robot, wherein the robot is a multi-joint mechanical arm, the robot has a base and an end, the robot can be set on a workbench or on the ground based on the base, and the end is used to connect an actuator; as well as A readable storage medium, wherein execution instructions are stored in the readable storage medium, and when the execution instructions are executed by a processor, they are used to implement the joint angle generation method for a robot as described in claim 1, and the robot performs inverse kinematics solution based on the execution instructions stored in the readable storage medium.

13. The robot system according to claim 12, characterized in that: The end is a flange.

14. The robot system according to claim 12, characterized in that: The actuator includes a manipulator capable of performing a grasping operation.

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