CN111216164A - Robot online calibration method, system, storage medium and calibration equipment - Google Patents
Robot online calibration method, system, storage medium and calibration equipment Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J19/00—Accessories fitted to manipulators, e.g. for monitoring, for viewing; Safety devices combined with or specially adapted for use in connection with manipulators
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J19/00—Accessories fitted to manipulators, e.g. for monitoring, for viewing; Safety devices combined with or specially adapted for use in connection with manipulators
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Abstract
The application provides a robot online calibration method, a system, a storage medium and a calibration device, wherein the method comprises the following steps: acquiring a plurality of joint angles of the robot at each position point and a coordinate measured value of the tail end of a robot tool at each position point in the process that the robot runs to K position points; carrying out iterative solution on the target equation set by using the obtained data to obtain the error values of the DH parameters and the joint zero positions; the target equation set is established in advance according to a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool; and correcting the DH parameters and the joint zero position of the robot by using the error value. The embodiment adopts on-line one-time calibration, and uses an iterative correction algorithm to directly calculate the corrected DH parameter value and the joint zero position, so that the robot does not need to be calibrated off-line, the on-line direct sampling point correction is realized, the operation is very convenient and fast, the implementation is easy, the speed is high, and the cost is low.
Description
Technical Field
The application relates to the technical field of robots, in particular to a robot online calibration method, a robot online calibration system, a storage medium and calibration equipment.
Background
With the continuous expansion of the machine loading amount and the application range of the industrial robot, the industry also puts higher demands on various aspects of the performance of the robot, wherein the positioning precision of the tail end of a robot tool is undoubtedly an important parameter index for evaluating the robot. The positioning accuracy of the robot generally includes pose accuracy (or absolute accuracy) and pose repeatability (or repeated positioning accuracy) of the robot.
With the increasing demands of visual application, offline programming and the like, the guarantee of the absolute accuracy of the robot needs to be further improved, and the assembly error of the robot in assembly and the abrasion and deformation in the use process affect the actual DH parameters and zero angle of the robot, so that the absolute positioning accuracy of the robot is reduced. At present, common robot zero position and DH parameter calibration methods are based on off-line calibration when leaving factory, for example, a joint zero position is calibrated through a mechanical reticle or an angle measuring instrument, the robot needs to be installed on a working platform through a base, and DH parameter deviation is controlled through accurately controlling machining and assembling precision of joint components, so that the method is high in cost and low in speed.
Disclosure of Invention
An object of the embodiments of the present application is to provide an online calibration method, system, storage medium and calibration device for a robot, which can realize online direct sampling point correction, and the robot does not need to be calibrated offline, and is very convenient and fast to operate, easy to implement, fast in speed and low in cost.
In a first aspect, an embodiment of the present application provides an online robot calibration method, including: in the process of acquiring K different position points of the robot in a working space, a plurality of joint angles of the robot at each position point recorded in a robot controller and a coordinate measured value of the tail end of a robot tool at each position point measured by space measuring equipment, wherein K is a positive integer; carrying out iterative solution on a target equation set by using the coordinate measurement values of the K position points, the plurality of joint angles, the coordinate theoretical values and the theoretical DH parameters to obtain error values of the DH parameters and joint zero positions; the target equation set is established in advance according to a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool; and correcting the DH parameters and the joint zero position of the robot by using the error value.
The technical scheme can be used for online calibration of robot DH parameters and zero positions, actual position information of K point positions in a robot space is acquired through space measuring equipment, corrected DH parameter values and joint zero positions are obtained very simply according to a target equation set established by a pose transfer matrix from a measuring coordinate system to the tail end of a robot tool, the robot does not need to be calibrated off line, and the robot does not need to be installed on a working platform through a base, so that online direct point acquisition and correction are realized, the operation is very convenient and fast, the implementation is easy, the speed is high, and the cost is low.
Optionally, before iteratively solving the objective equation set by using the coordinate measurement values, the plurality of joint angles, the coordinate theoretical values, and the theoretical DH parameters of the K position points, the method further includes: calculating a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool, and performing partial differential calculation on each unknown quantity in the matrix according to the pose transfer matrix to obtain an error transfer matrix; and establishing the target equation set according to the error transfer matrix.
According to the scheme, the error transfer matrix under the measurement coordinate system is directly calculated based on the pose transfer matrix, calculation is simplified, meanwhile, the robot on the production line can be directly calibrated, and specific installation is not needed.
Optionally, the target equation set is: x is A-1D; wherein X is a column vector composed of error values of all unknowns in the error transfer matrix, A-1Is the inverse of the matrix a and is,
D＝M-N；Ajsubstituting the joint angle and the theoretical DH parameter of the jth position point into the error transfer matrix to obtain a matrix; d is an error matrix formed by the position errors of the K position points, M is the coordinate measurement value of the K position points, and N is the coordinate theoretical value of the K position points.
Optionally, the calculating a pose transmission matrix from a measurement coordinate system of the spatial measurement device to the end of the robot tool includes:
calculating a pose transfer matrix from a robot base coordinate system to a robot tool end
Wherein the content of the first and second substances,
is a pose transfer matrix from a joint i-1 to a joint i, g is the number of joints of the robot,
a pose transfer matrix for the g-th joint end to the tool end of the robot, an
And
has the following relationship:
wherein, ailength of the connecting rod, alpha, from joint i-1 to joint iiThe torsional angle of the connecting rod of the joint i-1 and the joint i, diLink offset distance, θ, for joint i-1 to joint iiThe joint angle from joint i-1 to joint i; l, m and n are coordinates of a measuring point of the space measuring equipment under a g-axis coordinate system of the robot; the value range of i is 1-g, and the joint 0 represents a base of the robot;
calculating a pose transfer matrix J from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool:
wherein the content of the first and second substances,
to measure the coordinate system transformation matrix of the coordinate system to the robot-based coordinate system,
the method comprises the following steps: measuring the coordinate translation (o, p, q) from the coordinate system to the base coordinate system and the rotation angle (r) of the coordinate axesx,ry,rz)。
Optionally, the performing partial differential calculation on each unknown quantity in the matrix according to the pose transfer matrix to obtain an error transfer matrix includes: determining the error transfer matrix according to the following equation:
optionally, the iteratively solving the objective equation set by using the coordinate measurement values of the K position points, the plurality of joint angles, the coordinate theoretical value, and the theoretical DH parameter to obtain an error value of the DH parameter and a joint zero position includes: executing the following iterative process until the maximum value of error values in the column vector X is smaller than a preset threshold value, and obtaining error values of the DH parameters and the joint zero positions: during a first iteration, substituting the coordinate measurement values, the joint angles, the coordinate theoretical values and the theoretical DH parameters of the K position points into a target equation set for solving to obtain a DH parameter and a joint zero error value of the first iteration; wherein the plurality of joint angles and the theoretical DH parameters are initial theoretical values; and during the t-th iteration after the first iteration, adding the error values of the DH parameters and the joint zero positions obtained in the previous iteration to the theoretical values of the previous iteration to obtain the theoretical values of the current iteration, substituting the theoretical values of the current iteration into a target equation set for solving, and obtaining the error values of the DH parameters and the joint zero positions of the t-th iteration.
The above scheme is to perform iterative calculation on all error values in X, that is, the error value obtained by this calculation is added to the parameter itself, and then the error value is calculated as a known quantity for the next time until the calculated error quantity is smaller than a set threshold, and convergence is considered to be achieved. In addition, in the iteration process, the calculation is more accurate due to the fact that full-parameter iteration is performed based on DH parameters, joint zero positions and the like.
In a second aspect, an embodiment of the present application provides an online robot calibration system, including: the robot comprises a robot, a robot controller, a space measuring device and a calibration device, wherein a measuring point of the space measuring device is arranged at the tail end of a tool of the robot, and the space measuring device and the robot controller are both connected with the calibration device; the robot controller is used for controlling the robot to sequentially run to K different position points in a working space, and K is a positive integer; the space measuring equipment is used for measuring the coordinates of the tail end of the robot tool at each position point; the calibration device is used for acquiring a plurality of joint angles of the robot at each position point recorded in the robot controller and coordinate measurement values of the robot tool end at each position point measured by the space measurement device; carrying out iterative solution on a target equation set by using the coordinate measurement values of the K position points, the plurality of joint angles, the coordinate theoretical values and the theoretical DH parameters to obtain error values of the DH parameters and joint zero positions; the target equation set is established in advance according to a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool; the calibration equipment is also used for correcting the DH parameters and the joint zero position of the robot by using the error value.
Optionally, the calibration device is specifically configured to: calculating a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool, and performing partial differential calculation on each unknown quantity in the matrix according to the pose transfer matrix to obtain an error transfer matrix; and establishing the target equation set according to the error transfer matrix.
In a third aspect, an embodiment of the present application provides a storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the method according to the first aspect is performed.
In a fourth aspect, an embodiment of the present application provides a calibration apparatus, including: a processor, a memory and a bus, the memory storing machine-readable instructions executable by the processor, the processor and the memory communicating over the bus when the calibration device is run, the machine-readable instructions when executed by the processor performing the method of the first aspect.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
FIG. 1 is a schematic flow chart of a robot online calibration method according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of an online robot calibration system provided in an embodiment of the present application;
fig. 3 is a flowchart of an implementation of an online calibration method for a robot according to an embodiment of the present disclosure;
FIG. 4 is a schematic diagram showing the comparison of position errors of the robot at 50 position points in space before and after calibration;
FIG. 5 is a schematic diagram of an online robot calibration device according to an embodiment of the present disclosure;
fig. 6 is a schematic diagram of a calibration apparatus according to an embodiment of the present application.
Icon: 210-a spatial measurement device; 220-a robot; 230-a robot controller; 240-calibrate the device.
Detailed Description
The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.
The embodiment of the application provides a method for carrying out online calibration on DH parameters and joint zero-position parameters of a robot based on space measuring equipment, and the method is high in precision, high in speed and flexible to use, can be used for online rapid calibration without special tools, and can effectively improve the absolute precision of the robot. The technical scheme is introduced in principle, and then steps implemented in practical application are explained.
Fig. 1 is a schematic flowchart of an online calibration method for a robot according to an embodiment of the present disclosure, and as shown in fig. 1, the method includes the following steps:
step 110: the measuring points of the space measuring device are arranged at the end of the tool of the robot, and the space measuring device and the robot controller are respectively connected with the calibration device.
The space measuring device is used for measuring the actual position coordinates of the tail end of the robot tool, and a wire stretcher or a laser tracker can be used in specific implementation. In the embodiment, a laser tracker is taken as an example, the laser tracker is firstly arranged, a laser reflection target ball of the laser tracker is mounted at the tail end of a tool of a robot, the laser tracker and a robot controller are respectively in communication connection with a calibration device, and the calibration device can receive actual position coordinates of the tail end of the robot tool measured by the laser tracker and theoretical values recorded in the robot controller and correct DH parameters and joint zero positions of the robot through an algorithm based on received data.
Step 120: and the robot controller controls the robot to sequentially run to K different position points in the working space.
The robot is controlled to sequentially run to K different position points in the working space through online programming, wherein K is a positive integer, for example, 30-50 position points can be selected, and the number of the position points can be other values. And in the running process of the robot, the mirror surface of the laser reflection target ball is ensured to face the laser tracker when reaching each position point.
Step 130: the calibration device obtains coordinate measurements of the robot tool tip at each position point measured by the spatial measurement device and a plurality of joint angles of the robot at each position point recorded within the robot controller.
When the robot moves to each position point, the calibration equipment collects the coordinates (x) of the target ball measured by the laser tracker when the tail end of the robot tool moves to each position pointj,yj,zj) And a plurality of joint angles recorded in the robot controller when the robot reaches each position point, the present embodiment is mainly described by taking a series-type six-axis industrial robot as an example, but the algorithm principle thereof may be appliedApplicable to other types of robots. For a six-axis industrial robot, six joint angles are recorded in the robot controller: theta1(j)、θ2(j)、θ3(j)、θ4(j)、θ5(j)、θ6(j)Wherein j represents the jth position point and represents the angle of the six joints respectively under the pose of the jth position point, and j is less than or equal to K.
the DH parameter of the robot reflects the size of the robot body, the actual size of the processed robot possibly deviates from the design size, so that the positioning precision is reduced, and the deviation is obtained by solving the error value of the DH parameteriLink offset distance d of the ith jointiLink length a of the ith jointiAnd joint angle theta of the ith jointiThe parameters have theoretical values (also called nominal values in general) in the robot controller, and the present embodiment needs to solve errors caused by machining and manufacturing between the theoretical parameters and the robot real size, so as to correct the absolute accuracy of the robot. Target sphere coordinate (x)i,yi,zi) for coordinate measurements of the end of the robot tool, representing the actual position, the link torsion angle alphaiOffset distance d of connecting rodiLength of connecting rod aiAnd joint angle thetaithe theoretical DH parameters of the robot are shown, it should be noted that the joint angle of each joint of the robot may be different at each position point, and the torsion angle α of the connecting rodiOffset distance d of connecting rodiLength of connecting rod aithe position point of the robot is not changed and is a fixed parameter, so for the convenience of understanding, the embodiment will only use the torsion angle α of the connecting rodiOffset distance d of connecting rodiLength of connecting rod aiReferred to as DH parameters.
in step 130, the calibration apparatus also obtains the theoretical DH parameters recorded in the robot controller (i.e. the link torsion angle α)iOffset distance d of connecting rodiLength of connecting rod aiTheoretical values of) and the theoretical values of the coordinates of the robot when it reaches each position point. Wherein, because the theoretical DH parameter is a fixed parameter, only needs to be obtained from the robot controllerTaking once, and then not obtaining any more; the theoretical coordinate value may be obtained according to a position command sent by the robot controller to the robot, and in step 120, the robot controller sends the position command to the robot to instruct the robot to move to a corresponding position, and the theoretical coordinate value is a coordinate of a target position indicated in the position command, or may be calculated by a kinematic forward solution and coordinate transformation according to six joint angles and a theoretical DH parameter when the robot is at the position point, so as to obtain the theoretical coordinate value in the robot base system. And (4) calculating the coordinate pose of the tool tail end from the base coordinate system by using the known quantities of the joint angles and the connecting rod parameters, wherein the process is called a kinematics positive solution.
Step 140: the calibration equipment calculates a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool, and performs partial differential calculation on each unknown quantity in the matrix according to the pose transfer matrix to obtain an error transfer matrix.
Specifically, step 140 includes the following two steps:
(1) calculating a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool:
first, a pose transfer matrix from a robot base coordinate system to a robot tool end is calculated
wherein, ailength of the connecting rod, alpha, from joint i-1 to joint iiThe torsional angle of the connecting rod of the joint i-1 and the joint i, diLink offset distance, θ, for joint i-1 to joint iiThe joint angle from joint i-1 to joint i; l, m and n are coordinates of a measuring point of the space measuring equipment under a g-axis coordinate system of the robot, such as coordinates of a laser reflection target ball under a sixth axis coordinate system. The value range of i is 1 to g, and the joint 0 represents the base of the robot.
If the laser tracker is vertically arranged, the measurement coordinate system can be a coordinate system established by taking the center of the laser tracker as the coordinate origin and the vertical direction of the laser tracker as the z axis, the robot base coordinate system is a coordinate system established inside the robot, and the g-th axis coordinate system is a coordinate system established by taking the direction perpendicular to the mounting surface of the g-th joint of the robot as the z axis.
Then, a pose transmission matrix J from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool is calculated:
wherein the content of the first and second substances,
for measuring coordinate systemsA coordinate system transformation matrix to a robot base coordinate system,
six unknown parameters are included: measuring the coordinate translation amount (o, p, q) from the coordinate system to the base coordinate system, namely the coordinate difference value between the coordinate origin points of the two space coordinate systems; and the rotation angles (r) of the three coordinate axes between the two spatial coordinate systemsx,ry,rz)。
(2) Calculating an error transfer matrix according to the pose transfer matrix:
and performing partial differential calculation on each unknown quantity in the attitude transfer matrix to obtain an error coefficient of each unknown quantity, and forming an error transfer matrix dJ shown as follows:
step 150: and establishing a target equation set according to the error transfer matrix, and performing iterative solution on the target equation set by using the coordinate measurement values of the K position points, the plurality of joint angles, the coordinate theoretical value and the theoretical DH parameter to obtain an error value of the DH parameter and the joint zero position.
In the error transfer matrix dJ obtained in the step (2), the right side of the equal sign includes 33 error variables, which are denoted as column vectors X, and the following equation set is established according to the error transfer matrix:
wherein D is an error matrix formed by position errors of K position points, M is a coordinate measurement value of the K position points, and N is a coordinate theoretical value of the K position points, for example, if the robot is controlled to operate 50 position points, the error matrix D is represented as a 50 × 3 matrix; a. thejAnd X is a column vector consisting of error values of all unknown quantities in the error transfer matrix, wherein the matrix is obtained by substituting the joint angle and the theoretical DH parameter of the jth position point into the error transfer matrix.
Thus, a target system of equations is obtained:
X＝A-1·D；
wherein A is-1Is the inverse of matrix a. After the target equation set is obtained, the equation set can be solved, and the method for solving the error variable used herein can be applied to fitting solving methods such as a least square method and the like besides matrix inversion, pseudo-inversion and the like. The solution of the objective system of equations can be performed using the prior art and will not be described here.
It should be noted that in the present embodiment, in the process of solving X in the objective equation set, iterative solution calculation is used, that is, multiple rounds of iterative calculation are performed on the objective equation set.
Specifically, the following iterative process is executed until the maximum value of the error values in the column vector X is smaller than a preset threshold value, and then the error values of the DH parameter and the joint zero position at that time are obtained:
in the first iteration, joint angles and theoretical DH parameters of K position points in a working space are used as initial theoretical values and substituted into a target equation set, and a matrix A is calculated-1Meanwhile, substituting the coordinate measurement values and the coordinate theoretical values of the K position points into a target equation set, calculating an error matrix D, and performing fitting solution on the target equation set to obtain a column vector X of the first iteration1，X1The method comprises the steps of including 33 error variables, wherein the error variables include DH parameters and error values of joint zero positions;
at the time of the t-th iteration after the first iteration, the column vector X obtained in the previous iteration is addedt-1Adding the obtained deviation to the original theoretical value again, regarding the added value as a new theoretical value, substituting the new theoretical value as the theoretical value of the iteration of the current round into the target equation set again, and performing fitting solution on the target equation set to obtain the column vector X of the iteration of the t roundtObtaining the error values of the DH parameters and the joint zero positions of the t-th iteration; by continuously iteratively calculating the solution error, the obtained X will be more and more accurate.
When X is added to the theoretical value used in the previous round for the first time, X is added133 error values in (1) correspond to the initial principleAddition of theoretic values for X1Except for DH parameters and joint angle parameters (including transformation errors of a measurement coordinate system and a robot base coordinate system and pose transfer parameters from the g-th joint end to the tool end: l, m, n, o, p, q, r)x,ry,rz) The initial corresponding theoretical value of error of (2) is 0 by default.
And when the maximum value of the error values in the X is smaller than a preset threshold value, convergence is considered to be achieved, namely the error at the moment is considered to be accurate enough, the iterative calculation process can be stopped, and the error value of the DH parameter and the error value of the joint zero position at the moment are obtained and are used as the final error value of the DH parameter and the error value of the joint zero position.
Step 160: and correcting the DH parameters and the joint zero position of the robot by using the error values obtained by iterative solution.
And (3) adding the error value obtained by iterative solution in the step (150) with the initial theoretical value to obtain a DH parameter correction value and a joint zero correction value, and finishing correction on the absolute precision of the robot by using the DH parameter correction value and the joint zero correction value. Specifically, the DH parameter correction value and the joint zero-position correction value may be written into the robot controller, and the robot controller completes parameter calibration, or the DH parameter correction value may be written into the robot controller, and the joint zero-position correction value may be written into the joint, and the joint itself calibrates the zero position.
The above is a schematic introduction of the present technical solution, and the following is a description of the method steps implemented in practical application. Fig. 2 is a schematic diagram of an online robot calibration system provided in an embodiment of the present application, and as shown in fig. 2, the system includes: the system comprises a space measuring device 210, a robot 220, a robot controller 230 and a calibration device 240, wherein measuring points of the space measuring device 210 are arranged at the tool end of the robot 220, the space measuring device 210 is used for measuring actual position coordinates of the tool end of the robot, the space measuring device 210 can be a wire stretcher or a laser tracker, taking the laser tracker as an example, a laser reflection target ball of the laser tracker is arranged at the tool end of the robot 220, and in the running process of the robot 220, the mirror surface of the laser reflection target ball faces the laser tracker when reaching each position point. The space measuring device 210 and the robot controller 230 are both connected to a calibration device 240.
Fig. 3 is a flowchart of an implementation of an online calibration method for a robot according to an embodiment of the present application, where the method is illustrated in fig. 2, and includes the following steps:
step 310: and the robot controller controls the robot to sequentially run to K different position points in the working space.
Step 320: the calibration device obtains a plurality of joint angles recorded within the robot controller at each position point of the robot, and coordinate measurements of the robot tool tip at each position point measured by the spatial measurement device.
Step 330: and the calibration equipment carries out iterative solution on the target equation set by utilizing the coordinate measurement values of the K position points, the plurality of joint angles, the coordinate theoretical value and the theoretical DH parameter to obtain the error values of the DH parameter and the joint zero position.
The target equation set can be pre-established according to the description of the foregoing embodiment, and forms an iterative correction algorithm to be preset in the calibration device.
Step 340: and the calibration equipment calculates a DH parameter correction value and a joint zero correction value according to the error value, and writes the correction value into the robot controller to finish the robot parameter calibration.
The inventor tests and verifies that after the calibration method provided by the embodiment is adopted, the position error pairs of the robot at 50 position points in the space are shown in fig. 4, so that the calibration method provided by the embodiment can improve the absolute accuracy of the robot to a great extent, the positioning of the tail end of the robot tool is more accurate, and a better effect is achieved.
In summary, the robot online calibration method provided by this embodiment may be used for online calibration of DH parameters and zero positions of the robot, and directly solve the target equation set through measurement data of the laser tracker and theoretical data in the robot controller without binding the measurement coordinate system and the robot base coordinate system by a specific tool. In the implementation process, online one-time calibration is adopted, an iterative correction algorithm is applied, the position information of K point positions in the space of the robot is acquired through the laser tracker, the corrected DH parameter value and the joint zero position are directly calculated, the robot does not need to be calibrated offline, and the robot does not need to be installed on a working platform through a base, so that online direct point acquisition correction is realized, the operation is very convenient and fast, the implementation is easy, the speed is high, and the cost is low. Meanwhile, the iterative computation of the target equation set of the embodiment has higher precision, so that the number of position points which the robot must reach is not required to be specified, the point number range is wider, and the setting of the position point number K is more flexible.
It should be noted that the principle and target parameters of the online calibration method provided in this embodiment are not limited to the defined DH parameters, but may also be used for time-varying parameters that affect the absolute accuracy, such as deceleration ratio, friction force, etc., in addition, if a communication bridge is established between the space measurement device and the robot controller, the online calibration method may also be executed by the space measurement device or the robot controller, for example, the robot controller obtains a coordinate measurement value of the end of the robot tool from the space measurement device, performs iterative calculation using the coordinate measurement value and the joint angle, coordinate theoretical value, and theoretical DH parameter recorded by itself, and after calculating the error value, may calibrate the DH parameter and the zero position of the robot by itself according to the error value.
Based on the same inventive concept, the embodiment of the present application further provides an online robot calibration apparatus, which is configured in the calibration device and is used for performing all the method steps performed by the calibration device in the foregoing embodiments. Referring to fig. 5, the apparatus includes:
the data acquisition module 410 is used for acquiring a plurality of joint angles of the robot at each position point recorded in the robot controller and a coordinate measured value of the robot tool end at each position point measured by the space measuring equipment in the process that the robot runs to K different position points in the working space, wherein K is a positive integer;
an iterative calculation module 420, configured to perform iterative solution on the objective equation set by using the coordinate measurement values of the K position points, the plurality of joint angles, the coordinate theoretical value, and the theoretical DH parameter, so as to obtain an error value of the DH parameter and a joint zero position; the target equation set is established in advance according to a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool;
and the parameter correcting module 430 is used for correcting the DH parameters and the joint zero positions of the robot by using the error values.
Optionally, the apparatus further comprises: the system comprises an equation set establishing module, a pose transfer matrix calculating module and an error transfer matrix calculating module, wherein the equation set establishing module is used for calculating a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool and performing partial differential calculation on each unknown quantity in the matrix according to the pose transfer matrix to obtain an error transfer matrix; and establishing the target equation set according to the error transfer matrix.
The above-mentioned robot online calibration apparatus is used for executing all the method steps implemented by the calibration device in the foregoing embodiment, and the basic principle and the generated technical effect are the same as those of the previous method embodiment.
Fig. 6 shows a possible structure of a calibration apparatus 240 provided in an embodiment of the present application. Referring to fig. 6, the calibration apparatus 240 includes: a processor 510, a memory 520, and a communication interface 530, which are interconnected and in communication with each other via a communication bus 540 and/or other form of connection mechanism (not shown).
The Memory 520 includes one or more (Only one is shown in the figure), which may be, but not limited to, a Random Access Memory (RAM), a Read Only Memory (ROM), a Programmable Read-Only Memory (PROM), an Erasable Read-Only Memory (EPROM), an electrically Erasable Read-Only Memory (EEPROM), and the like. The processor 510, as well as possibly other components, may access, read, and/or write data to the memory 520.
The processor 510 includes one or more (only one shown) which may be an integrated circuit chip having signal processing capabilities. The Processor 510 may be a general-purpose Processor, and includes a Central Processing Unit (CPU), a Micro Control Unit (MCU), a Network Processor (NP), or other conventional processors; or a special-purpose Processor, including a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, a discrete Gate or transistor logic device, and a discrete hardware component.
One or more computer program instructions may be stored in the memory 520 and read and executed by the processor 510 to implement the steps of the robot online calibration method provided by the embodiments of the present application and other desired functions.
It will be appreciated that the configuration shown in fig. 6 is merely illustrative and that the calibration device 240 may also include more or fewer components than shown in fig. 6, or have a different configuration than shown in fig. 6. The components shown in fig. 6 may be implemented in hardware, software, or a combination thereof.
The embodiment of the present application further provides a computer-readable storage medium, where computer program instructions are stored on the computer-readable storage medium, and when the computer program instructions are read and executed by a processor of a computer, the steps of the robot online calibration method provided in the embodiment of the present application are executed. For example, a computer readable storage medium may be implemented as memory 520 in calibration device 240 in FIG. 6.
The embodiment of the present application further provides a computer program product, which when running on a computer, causes the computer to execute the robot online calibration method provided in the embodiment.
In the embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units is only one logical division, and there may be other divisions when actually implemented, and for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection of devices or units through some communication interfaces, and may be in an electrical, mechanical or other form.
Furthermore, the functional modules in the embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.
It should be noted that the functions, if implemented in the form of software functional modules and sold or used as independent products, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application or portions thereof that substantially contribute to the prior art may be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
The above description is only an example of the present application and is not intended to limit the scope of the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (10)
1. An on-line robot calibration method is characterized by comprising the following steps:
in the process of acquiring K different position points of the robot in a working space, a plurality of joint angles of the robot at each position point recorded in a robot controller and a coordinate measured value of the tail end of a robot tool at each position point measured by space measuring equipment, wherein K is a positive integer;
carrying out iterative solution on a target equation set by using the coordinate measurement values of the K position points, the plurality of joint angles, the coordinate theoretical values and the theoretical DH parameters to obtain error values of the DH parameters and joint zero positions; the target equation set is established in advance according to a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool;
and correcting the DH parameters and the joint zero position of the robot by using the error value.
2. The method of claim 1, wherein prior to iteratively solving a system of objective equations using the coordinate measurements, the plurality of joint angles, coordinate theoretical values, and theoretical DH parameters for K position points, the method further comprises:
calculating a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool, and performing partial differential calculation on each unknown quantity in the matrix according to the pose transfer matrix to obtain an error transfer matrix;
and establishing the target equation set according to the error transfer matrix.
3. The method of claim 2, wherein the target system of equations is:
X＝A-1·D；
wherein X is the errorA column vector formed by error values of all unknowns in the transfer matrix, A-1Is the inverse of the matrix a and is,
D＝M-N；Ajsubstituting the joint angle and the theoretical DH parameter of the jth position point into the error transfer matrix to obtain a matrix; d is an error matrix formed by the position errors of the K position points, M is the coordinate measurement value of the K position points, and N is the coordinate theoretical value of the K position points.
4. The method of claim 3, wherein the computing a pose transfer matrix of a measurement coordinate system of the spatial measurement device to a robotic tool tip comprises:
calculating a pose transfer matrix from a robot base coordinate system to a robot tool end
Wherein the content of the first and second substances,
is a pose transfer matrix from a joint i-1 to a joint i, g is the number of joints of the robot,
a pose transfer matrix for the g-th joint end to the tool end of the robot, an
And
has the following relationship:
wherein, ailength of the connecting rod, alpha, from joint i-1 to joint iiThe torsional angle of the connecting rod of the joint i-1 and the joint i, diLink offset distance, θ, for joint i-1 to joint iiThe joint angle from joint i-1 to joint i; l, m and n are coordinates of a measuring point of the space measuring equipment under a g-axis coordinate system of the robot; the value range of i is 1-g, and the joint 0 represents a base of the robot;
calculating a pose transfer matrix J from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool:
wherein the content of the first and second substances,
to measure the coordinate system transformation matrix of the coordinate system to the robot-based coordinate system,
the method comprises the following steps: measuring the coordinate translation (o, p, q) from the coordinate system to the base coordinate system and the rotation angle (r) of the coordinate axesx,ry,rz)。
5. The method according to claim 4, wherein the partial differential calculation of each unknown quantity in the matrix according to the pose transfer matrix to obtain an error transfer matrix comprises:
determining the error transfer matrix according to the following equation:
6. the method of claim 5, wherein iteratively solving a set of objective equations using the coordinate measurements, the plurality of joint angles, coordinate theoretical values, and theoretical DH parameters for K position points to obtain an error value for a DH parameter and a joint null, comprises:
executing the following iterative process until the maximum value of error values in the column vector X is smaller than a preset threshold value, and obtaining error values of the DH parameters and the joint zero positions:
during a first iteration, substituting the coordinate measurement values, the joint angles, the coordinate theoretical values and the theoretical DH parameters of the K position points into a target equation set for solving to obtain a DH parameter and a joint zero error value of the first iteration; wherein the plurality of joint angles and the theoretical DH parameters are initial theoretical values;
and during the t-th iteration after the first iteration, adding the error values of the DH parameters and the joint zero positions obtained in the previous iteration to the theoretical values of the previous iteration to obtain the theoretical values of the current iteration, substituting the theoretical values of the current iteration into a target equation set for solving, and obtaining the error values of the DH parameters and the joint zero positions of the t-th iteration.
7. An online robot calibration system, comprising: the robot comprises a robot, a robot controller, a space measuring device and a calibration device, wherein a measuring point of the space measuring device is arranged at the tail end of a tool of the robot, and the space measuring device and the robot controller are both connected with the calibration device;
the robot controller is used for controlling the robot to sequentially run to K different position points in a working space, and K is a positive integer;
the space measuring equipment is used for measuring the coordinates of the tail end of the robot tool at each position point;
the calibration device is used for acquiring a plurality of joint angles of the robot at each position point recorded in the robot controller and coordinate measurement values of the robot tool end at each position point measured by the space measurement device; carrying out iterative solution on a target equation set by using the coordinate measurement values of the K position points, the plurality of joint angles, the coordinate theoretical values and the theoretical DH parameters to obtain error values of the DH parameters and joint zero positions; the target equation set is established in advance according to a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool;
the calibration equipment is also used for correcting the DH parameters and the joint zero position of the robot by using the error value.
8. The system of claim 7, wherein the calibration device is specifically configured to: calculating a pose transfer matrix from a measurement coordinate system of the space measurement equipment to the tail end of the robot tool, and performing partial differential calculation on each unknown quantity in the matrix according to the pose transfer matrix to obtain an error transfer matrix; and establishing the target equation set according to the error transfer matrix.
9. A storage medium, characterized in that the storage medium has stored thereon a computer program which, when being executed by a processor, performs the method according to any one of claims 1-6.
10. A calibration device, comprising: a processor, a memory and a bus, the memory storing machine-readable instructions executable by the processor, the processor and the memory communicating over the bus when the calibration device is run, the machine-readable instructions when executed by the processor performing the method of any of claims 1-6.
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