CN115533893A - Robot TCP calibration method using floatable standard sphere - Google Patents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/16—Programme controls
- B25J9/1679—Programme controls characterised by the tasks executed
- B25J9/1692—Calibration of manipulator
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/16—Programme controls
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/16—Programme controls
- B25J9/1694—Programme controls characterised by use of sensors other than normal servo-feedback from position, speed or acceleration sensors, perception control, multi-sensor controlled systems, sensor fusion
- B25J9/1697—Vision controlled systems
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Abstract
A robot TCP calibration method using a floatable standard sphere comprises the following steps: measuring the coordinates of the center of the floatable standard ball in the robot base coordinate system in a non-external force state through binocular stereo vision; controlling the robot to contact the TCP with the standard sphere for more than three times in different postures, recording the joint rotation angle information of the robot during contact, and measuring the descending height of the standard sphere during contact; according to the measured robot joint corner information, the coordinates of the standard ball in the no-external-force state and the descending height of the standard ball when in contact, the target function is established by combining the structural parameters of the robot, the coordinates of the TCP in the robot flange coordinate system are calculated through nonlinear optimization solution, and the calibration precision is evaluated. The calibration method does not need the TCP point of the robot to coincide with the same fixed point for many times, weakens the requirement of point-point coincidence into point-surface coincidence, and simultaneously avoids the collision of the TCP and the outside. When the TCP of the robot has small deviation, the automatic calibration can be realized.
Description
Technical Field
The invention relates to a robot tool center point calibration method, in particular to a robot tool center point calibration method utilizing an industrial camera and a floatable standard sphere.
Background
With the rapid development of modern industry and the introduction of the concept of "industrial 4.0", people have higher and higher requirements on industrial production. As an important part of industrial production, robots are receiving more and more attention due to their advantages in terms of production efficiency, work accuracy, cost, and the like. It is well known that robots require an actuator or tool to be mounted to their end prior to operation. In order to enable the robot to work normally, the position of the central point of the robot tool relative to the flange plate of the robot needs to be acquired, and TCP calibration is carried out. In the industrial production process, if the tool is worn or bent due to long-term use of the tool, the production quality and the working efficiency of the robot are greatly influenced. Therefore, the research of the method for rapidly and accurately calibrating the center point of the on-line tool has important significance for improving the positioning precision of the robot, expanding the application market of the robot and improving the intellectualization and flexibility of the robot.
The traditional robot TCP calibration method is mainly based on the robot body to calibrate the TCP, and the calibration method requires that the robot enables the TCP to coincide with a fixed point in space through four different directions, and the TCP calibration value is obtained through calculating the positions and postures of the flange plates relative to the robot base coordinate system under the four point states. However, the method has the problems that the point and the point are required to be manually controlled to coincide, the calibration precision is poor if the point and the point are not accurately aligned in the process of coinciding and adjusting, a reference object can be collided to damage a tool in the adjusting process, and the calibration method is only suitable for being carried out in an off-line state and cannot realize on-line calibration.
Disclosure of Invention
The invention provides a robot TCP calibration method using a floatable calibration sphere, aiming at overcoming the defect that the traditional robot TCP calibration cannot take calibration precision and calibration efficiency into consideration.
The invention assists the robot TCP calibration work by utilizing the industrial camera with the binocular positioning function and the standard sphere with the known vertical floating radius, avoids the damage to tools in the calibration process, improves the calibration efficiency and is easy to realize the automation of calibration.
The method is based on a standard sphere with known vertical floating radius, firstly, the coordinate of the center of the sphere in a robot base coordinate system under the condition that the standard sphere has no external force is obtained through an industrial camera, the tool center point of the robot is made to contact the standard sphere for multiple times through operating the robot, the descending height of the standard sphere and the corner information of each joint of the robot during contact are recorded, an objective function is established according to the constant and known radius of the standard sphere by combining the self structural information of the robot, and the coordinate of the tool center point of the robot in a robot flange plate coordinate system is obtained through a Levenberg-Marquardt nonlinear optimization method so as to achieve the purpose of TCP calibration.
A robot TCP calibration method using a floating standard ball comprises the following steps:
(1) Firstly, the coordinates of the sphere center of a standard sphere in a robot base coordinate system under the state of no external force are obtained through an industrial camera.
Three cameras are placed in a regular triangle, a floatable standard sphere is placed at the outer center of the triangle, the whole device is horizontally placed in a robot working space, optical axes of the cameras are intersected with a sphere, a binocular stereo vision system is established through binocular correction, the position of the sphere center without external force in a camera coordinate system is identified and positioned, a coordinate transformation relation between the camera coordinate system and a robot base coordinate system is established through hand-eye calibration, and then the coordinate transformation relation of the sphere center in the robot base coordinate system is obtained b P s 。
(2) Controlling the robot to contact the central point of a tool of the robot with the upper hemisphere of the standard sphere in different postures, and recording the descending height of the standard sphere and the rotation angle of each joint of the robot during contact;
wherein the contact is made while keeping the extension of the end tool as far as possible through the center of the sphere.
During contact, the pose of a flange plate coordinate system relative to a robot base coordinate system can be represented by combining the rotation angles of all joints of the robot with the self structure of the robot and the original point of the robot base coordinate system, and the coordinates of a contact point in the robot base coordinate system, namely the coordinates of a tool center point in the robot base coordinate system, are represented by combining TCP information;
coordinates of the robot tool center point in a robot-based coordinate system { B } b P tcp Coordinates in a robot flange plate coordinate system { E } e P tcp The relationship between them is as follows:
wherein the content of the first and second substances, b T e is the coordinate of the origin of the robot flange plate coordinate system { E } in the robot base coordinate system { B }, theta is the rotation angle of each joint of the robot, and theta = { theta = { (theta) } 1 ,θ 2 ,θ 3 ,θ 4 ,θ 5 ,θ 6 } T ，
The rotation matrix of the robot flange coordinate system { E } relative to the robot base coordinate system { B } is determined by the rotation angle of each joint of the robot and the structural parameters of the robot.
The number of the contact points is k (k is larger than or equal to 3), and the common area where the contact points are located in the visual fields of the two cameras is specified.
(3) And acquiring the coordinates of the contact point in a camera coordinate system through binocular stereo vision, and recording.
(4) Establishing an objective function under the condition that the distance between the contact point and the sphere center of the standard sphere is equal to the radius, and solving and obtaining the coordinate of the robot tool center point in the robot flange coordinate system by a nonlinear optimization method e P tcp ＝{ e x tcp , e y tcp , e z tcp } T Completing calibration;
the distance between the center point of the robot tool and the coordinates of the sphere center in the robot base coordinate system is equal to the radius of the standard sphere, and when the contact is performed for the ith time (i =1,2, \8230;, k), the coordinates of the contact point in the robot base coordinate system are determined b P tcp i Coordinates of the center of sphere b P s i The vectors of composition are:
the following objective functions are established by utilizing the constraint relation of invariable standard spherical radius:
wherein, the first and the second end of the pipe are connected with each other, b P tcp i coordinates of the contact point in a robot base coordinate system { B }; b P s i is the coordinate of the sphere center in the robot base coordinate system { B } when in contact;
is a contact point b P tcp i A rotation matrix of the corresponding robot flange plate coordinate system relative to the robot base coordinate system { B }; b T e i is a contact point b P tcp i Coordinates of the origin of the corresponding robot flange plate coordinate system { E } in the robot base coordinate system { B }; b P s the coordinate of the sphere center of the standard sphere without external force in a robot base coordinate system { B }; d i ＝[0 0 d i ] T For contact, the coordinates of the centre of the sphere of the standard sphere are transformed, since here the floatable standard sphere, only the downward shift in the z-direction is present, here d i The height of the descending of the center of the standard sphere is taken as the height of the descending of the center of the standard sphere; r is the radius value of a standard sphere.
Optimizing and solving by a Levenberg-Marquardt nonlinear optimization method, and when the function converges to a solution e P tcp ＝{ e x tcp , e y tcp , e z tcp } T And when the objective function value at the solution is smaller than the threshold epsilon, the current calibration result is shown to meet the precision requirement, and the calibration is successful.
(5) After the robot works for a period of time, the tool may be worn or bent, so that the position of the TCP is inaccurate, the TCP can be corrected in an online state, and the PC endTransmitting to the robot the information on the rotational angle of each joint of the robot at the time of contact in step (2) = { theta = { theta = } 1 ,θ 2 ,θ 3 ,θ 4 ,θ 5 ,θ 6 } T The robot runs to a corresponding corner, whether a tool center point is in contact with a standard sphere or not is judged, if not, the coordinate of the tool center point in a camera coordinate system is located through a binocular stereo vision system, the position deviation of the tool center point in the camera coordinate system needs to be obtained through calculation twice, the position deviation is sent to the robot, the tool center point is guided to be in contact with the standard sphere, and corner information of each joint of the robot and descending height information of the standard sphere during contact are recorded.
Substituting the corner information of each joint and the descending height information of the standard ball during contact by the objective function established in the step (4), and solving the coordinate of the central point of the new robot tool in the flange coordinate system through nonlinear optimization e P tcp ＝{ e x tcp , e y tcp , e z tcp } T And verifying whether the calibration result meets the precision requirement.
But standard spheroid of floating comprises a standard ball and a platform that can measure and derive decline information, if no exogenic action, and the standard ball is in same position all the time, if exogenic action, platform and standard ball decline, and descending height is as the basis of judging the contact, is the contact when d >0 promptly, is contactless when d =0, has guaranteed the sufficiency of contact for when the contact of robot utensil central point and standard spheroid, automated inspection contact signal realizes the automatic control of calibration process.
The invention provides a robot tool center point calibration method by using a standard sphere with a known floatable radius, which comprises the steps of firstly obtaining the coordinates of the center of the standard sphere in a robot base coordinate system under the action of no external force through binocular stereo vision, then controlling a robot to contact the center of a robot tool with the standard sphere in different postures so as to descend the standard sphere, and recording the descending height of the standard sphere and the corner information of each joint of the robot during contact; secondly, establishing an objective function under the condition that the distance between the contact point and the sphere center of the standard sphere is equal to the radius, and solving and obtaining the coordinate of the robot tool center point in a robot flange coordinate system by a Levenberg-Marquardt nonlinear optimization method; the calibration of the robot TCP is realized by utilizing the standard sphere with known floatable radius, the point-point coincidence process which is difficult to realize accurately under the conditions of visual observation and manual control is avoided, the robot TCP does not need to coincide with the same point in space for many times, the collision of the TCP and the spherical surface is avoided while the floatability of the sphere weakens the point-point coincidence requirement into point-surface coincidence, the damage of the calibration process to a tool is reduced, and the operation is simple. When the TCP of the robot has small deviation, the planning point is corrected through the binocular stereoscopic vision system, so that the robot can still make the TCP contact with the floatable calibration ball according to a preset program, and online calibration is realized. The whole method is easy to operate, ingenious in conception, high in calibration precision and good in popularization effect.
The invention has the advantages that: the method has the advantages that the operation is easy, the calibration precision is high, the TCP point of the robot does not need to be overlapped with the same fixed point for multiple times, the point-point overlapping requirement is weakened into point-surface overlapping, and meanwhile, the collision between the TCP and the outside is avoided; when the TCP of the robot has small deviation, the autonomous calibration can be realized.
Drawings
FIG. 1 is a schematic diagram of a robot, a camera and a floatable standard sphere with a measurable descending height used in the method of the present embodiment.
Description of reference numerals: 1-fixed robot base, 2-six degree of freedom robot, 3-tool with tip attribute, 4-industrial camera, 5-floatable standard sphere, 6-computer, 7-robot controller.
Fig. 2 is a schematic diagram of the center point contact of the tool with a floatable standard ball in this example.
Fig. 3 is a top view of the contact point on a standard sphere in this example, area 1 is the common area of the view angles of camera 1 and camera 2, area 2 is the common area of camera 1 and camera 3, and area 3 is the common area of camera 2 and camera 3.
Detailed Description
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
Examples
Fig. 1 is a schematic diagram of a robot, a camera and a floatable standard sphere with a measurable descending height, which are used in the embodiment of the present invention, including a robot base 1, a six-degree-of-freedom robot 2, a tool 3 with a tip attribute, an industrial camera 4 and a floatable standard sphere 5.
As shown in fig. 2, the floatable standard sphere has a known radius, moves only vertically, does not move in a horizontal plane, and drops to a measurable height.
As shown in FIG. 3, the three cameras are placed in a regular triangle, the floating calibration sphere is placed at the outer center of the regular triangle, and the contact points fall in the common visual field range of the two cameras, namely, the area 1, the area 2 and the area 3.
Wherein, { C } is a camera coordinate system, { B } is a robot base coordinate system established in the space where the robot base is located, and { E } is a flange plate coordinate system established in the space where the flange plate at the end of the robot is located, and a computer 6 is used for collecting a signal of the standard ball descending height and judging whether the tool center point contacts the standard ball. The computer is connected with the robot controller 7 through a network, and can send a stop signal to the robot when the standard sphere has a touch signal, and read the information of the corner joint of the robot and the descending information of the standard sphere.
(1) The coordinates of the sphere center in the camera coordinate system under the condition of no external force action of the floatable standard sphere are identified and positioned through a binocular stereoscopic vision system established between every two three cameras, and the coordinates of the sphere center in the robot base coordinate system under the condition of no external force action are obtained through the hand-eye calibration result b P s 。
But floatable standard spheroid and industry camera, the level is fixed in the arbitrary position within the robot work space, when the contact of robot tool central point at every turn, but floatable standard spheroid only can move perpendicularly downwards, the position does not change in the horizontal space, the height that descends downwards can direct measurement derive.
(2) Controlling the robot to contact a tool center point of the robot with the upper hemisphere of a standard sphere in different postures, wherein the contact points are uniformly distributed in a common area of every two cameras in the sphere, as shown in fig. 3, keeping the extension line of the tool to pass through the center of the sphere as much as possible during contact, as shown in fig. 2, recording the descending height of the standard sphere and the rotation angle of each joint of the robot during contact, and acquiring the coordinates of the contact points in a camera coordinate system through a binocular stereoscopic vision system;
reading standard ball descent height d from floatable standard ball platform 1 Reading a current joint rotation angle theta from the robot controller 1 ＝{θ 1 1 ,θ 2 1 ,θ 3 1 ,θ 4 1 ,θ 5 1 ,θ 6 1 } T ；
The coordinates of the contact in the robot base coordinate system, namely the coordinates of the tool center point in the robot base coordinate system, can be obtained through the corners of all joints of the robot, the tool structure and the origin of the robot base coordinate system;
and (3) controlling the central point of the robot tool to be far away from the standard sphere, adjusting the posture to contact the second planning contact point shown in the figure 3, and stopping the robot after the standard sphere senses the touch. Obtaining the descending height d of a standard sphere 2 And rotation angle information theta of each joint of the robot 2 ＝{θ 1 2 ,θ 2 2 ,θ 3 2 ,θ 4 2 ,θ 5 2 ,θ 6 2 } T ；
Repeating the third point of the operation contact planning again to obtain the descending height d of the standard sphere 3 Angle of rotation theta of each joint of robot 3 ＝{θ 1 3 ,θ 2 3 ,θ 3 3 ,θ 4 3 ,θ 5 3 ,θ 6 3 } T 。
The number of the contact points is k (k is more than or equal to 3), k =3 is selected, and the formed contact points are uniformly distributed in a common visual field area of every two cameras on the sphere, as shown in fig. 3.
Coordinates of the robot tool center point in a robot-based coordinate system { B } b P tcp Coordinate system of robot flangeCoordinates in { E } e P tcp The relationship between them is as follows:
wherein the content of the first and second substances, b T e is the coordinate of the origin of the robot flange plate coordinate system { E } in the robot base coordinate system { B }, theta is the rotation angle of each joint of the robot, and theta = { theta = } 1 ,θ 2 ,θ 3 ,θ 4 ,θ 5 ,θ 6 } T ，
The rotation matrix of the robot flange coordinate system { E } relative to the robot base coordinate system { B } is determined by the rotation angle of each joint of the robot and the structural parameters of the robot.
(3) And in the contact process, acquiring the coordinates of the contact point in a camera coordinate system through binocular stereo vision, and recording.
(4) Establishing an objective function by utilizing the radius equal to the distance between any contact point and the sphere center of the standard sphere, and solving and obtaining the coordinate of the robot tool center point in the robot flange coordinate system by a nonlinear optimization method e P tcp ＝{ e x tcp , e y tcp , e z tcp } T Completing calibration;
the distance between the center point of the tool and the center of the sphere in the robot base coordinate system is equal to the radius of the standard sphere during the contact, and the contact point coordinate in the robot base coordinate system is at the ith contact (i =1,2, \8230; k) b P tcp i Coordinates of the center of sphere b P s i The vector of composition is:
the following objective function was established using standard spherical radii invariant and known:
wherein the content of the first and second substances, b P tcp i coordinates of the contact point in a robot base coordinate system { B }; b P s i is the coordinate of the sphere center in the robot base coordinate system { B } when in contact;
is a contact point b P tcp i A rotation matrix of the corresponding robot flange plate coordinate system relative to the robot base coordinate system { B }; b T e i is a contact point b P tcp i Coordinates of the origin of the corresponding robot flange plate coordinate system { E } in the robot base coordinate system { B }; b P s the coordinate of the sphere center of the standard sphere without external force in a robot base coordinate system { B }; d i ＝[0 0 d i ] T For contact, the coordinates of the centre of the sphere of the standard sphere are transformed, since here the floatable standard sphere, only the downward shift in the z-direction is present, here d i The height of the center of the standard sphere is reduced; r is the radius value of a standard sphere.
By using a Matlab optimization tool box and adopting a Levenberg-Marquardt nonlinear optimization method to optimize and solve, when the function converges to the solution e P tcp ＝{ e x tcp , e y tcp , e z tcp } T And when the objective function value at the solution is smaller than the threshold epsilon, the current calibration result is shown to meet the precision requirement, and the calibration is successful.
(5) After the robot works for a period of time, the tool may be worn or bent, so that the position of the TCP is inaccurate, at this time, the TCP can be corrected in an online state, and the PC sends information θ = { θ = of the joint angle of the robot in the step (2) when the robot is in contact with the tool to the robot 1 ,θ 2 ,θ 3 ,θ 4 ,θ 5 ,θ 6 } T When each joint of the robot runs to a corresponding corner, the floatable standard ball judges the central point of the tool through the falling heightAnd if the tool center point is not in contact with the standard sphere, positioning the coordinate of the tool center point in a camera coordinate system through a binocular stereo vision system, calculating to obtain the position deviation of the tool center point in the camera coordinate system before and after the TCP is changed, sending the position deviation to the robot, guiding the tool center point to be in contact with the standard sphere, and recording the information of each joint angle of the robot and the descending height information of the standard sphere during contact.
When the point contact of k (k is more than or equal to 3) is completed, substituting the corner information of each joint and the descending height information of the standard ball during the contact through the objective function established in the step (4), and solving out the coordinate of the new robot tool center point in the flange coordinate system through nonlinear optimization e P tcp ＝{ e x tcp , e y tcp , e z tcp } T And verifying whether the calibration result meets the precision requirement.
Compared with the traditional four-point calibration method, the calculated calibration result has better consistency with the traditional four-point calibration method, meanwhile, due to the floatability of the standard ball, the tool can be well protected during calibration, and when the TCP of the robot has smaller offset, the planning point is corrected through the binocular stereoscopic vision system, so that the robot can generally ensure that the TCP is in contact with the floatable standard ball according to a preset program, and the autonomous calibration is realized.
The above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and those skilled in the art can make modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (3)
1. A robot TCP calibration method using a floating standard ball comprises the following steps:
(1) Firstly, the coordinates of the sphere center of a standard sphere in a robot base coordinate system under the state of no external force are obtained through an industrial camera.
Three cameras are placed in a regular triangle, a floatable standard ball is placed at the outer center of the triangle, and the whole device is horizontally placed on the robotIn a working space, the optical axis of a camera intersects with a sphere, a binocular stereo vision system is established through binocular correction, the position of the sphere center under the action of no external force in a camera coordinate system is identified and positioned, the coordinate transformation relation between the camera coordinate system and a robot base coordinate system is established through hand-eye calibration, and then the coordinate of the sphere center in the robot base coordinate system is obtained b P s 。
(2) Controlling the robot to contact the central point of a tool of the robot with the upper hemisphere of the standard sphere in different postures, and recording the descending height of the standard sphere and the rotation angle of each joint of the robot during contact;
wherein the contact is made while keeping the extension of the end tool as far as possible through the center of the sphere.
During contact, the pose of a flange plate coordinate system relative to a robot base coordinate system can be represented by combining the rotation angles of all joints of the robot with the self structure of the robot and the original point of the robot base coordinate system, and the coordinates of a contact point in the robot base coordinate system, namely the coordinates of a tool center point in the robot base coordinate system, are represented by combining TCP information;
coordinates of the robot tool center point in a robot-based coordinate system { B } b P tcp Coordinates in a robot flange plate coordinate system { E }) e P tcp The relationship between them is as follows:
wherein the content of the first and second substances, b T e is the coordinate of the origin of the robot flange plate coordinate system { E } in the robot base coordinate system { B }, theta is the rotation angle of each joint of the robot, and theta = { theta = { (theta) } 1 ,θ 2 ,θ 3 ,θ 4 ,θ 5 ,θ 6 } T ，
The rotation matrix of the robot flange coordinate system { E } relative to the robot base coordinate system { B } is determined by the rotation angle of each joint of the robot and the structural parameters of the robot.
The number of the contact points is k (k is larger than or equal to 3), and the common area where the contact points are located in the visual fields of the two cameras is specified.
(3) And acquiring the coordinates of the contact point in a camera coordinate system through binocular stereo vision, and recording.
(4) Establishing an objective function under the condition that the distance between the contact point and the sphere center of the standard sphere is equal to the radius, and solving and obtaining the coordinate of the robot tool center point in the robot flange coordinate system by a nonlinear optimization method e P tcp ＝{ e x tcp , e y tcp , e z tcp } T Completing calibration;
the distance between the center point of the robot tool and the coordinates of the sphere center in the robot base coordinate system is equal to the radius of the standard sphere, and the coordinate of the contact point in the robot base coordinate system is equal to the radius of the standard sphere when the contact is performed for the ith time (i =1,2, \ 8230;, k) b P tcp i Coordinates of the center of sphere b P s i The vectors of composition are:
the following objective functions are established by utilizing the constraint relation of invariable standard spherical radius:
wherein the content of the first and second substances, b P tcp i coordinates of the contact point in a robot base coordinate system { B }; b P s i is the coordinate of the sphere center in the robot base coordinate system { B } when in contact;
is a contact point b P tcp i A rotation matrix of the corresponding robot flange plate coordinate system relative to the robot base coordinate system { B }; b T e i is a contact point b P tcp i Coordinates of the origin of the corresponding robot flange plate coordinate system { E } in the robot base coordinate system { B }; b P s the coordinate of the sphere center of the standard sphere without external force in a robot base coordinate system { B }; d i ＝[0 0 d i ] T For contact, the coordinates of the centre of the sphere of the standard sphere are transformed, since here the floatable standard sphere, only the downward shift in the z-direction is present, here d i The height of the center of the standard sphere is reduced; and R is the radius value of a standard sphere.
Optimizing and solving by a Levenberg-Marquardt nonlinear optimization method, and when a function converges to a solution e P tcp ＝{ e x tcp , e y tcp , e z tcp } T And when the objective function value at the solution is smaller than the threshold epsilon, the current calibration result is shown to meet the precision requirement, and the calibration is successful.
(5) After the robot works for a period of time, the tool may be worn or bent, so that the position of the TCP is inaccurate, at this time, the TCP may be corrected in an online state, and the PC sends information θ = { θ = each joint angle of the robot when the robot makes contact in step (2) to the robot 1 ,θ 2 ,θ 3 ,θ 4 ,θ 5 ,θ 6 } T And the robot runs to a corresponding corner, whether the tool center point is in contact with the standard sphere is judged, if not, the coordinate of the tool center point in the camera coordinate system is positioned through a binocular stereo vision system, the position deviation of the tool center point in the camera coordinate system needs to be obtained twice through calculation, the position deviation is sent to the robot, the tool center point is guided to be in contact with the standard sphere, and the corner information of each joint of the robot and the descending height information of the standard sphere during contact are recorded.
Substituting the corner information of each joint and the descending height information of the standard ball during contact by the objective function established in the step (4), and solving the coordinate of the new central point of the robot tool in the flange coordinate system by nonlinear optimization e P tcp ＝{ e x tcp , e y tcp , e z tcp } T And verifying whether the calibration result meets the requirement of precisionAnd (5) obtaining.
The floatable standard sphere consists of a standard sphere and a platform capable of measuring and deriving descending information, if no external force action exists, the standard sphere is always in the same position, if the external force action exists, the platform and the standard sphere descend, the descending height serves as a basis for judging contact, namely, the standard sphere is in contact when d is greater than 0, and the standard sphere is not in contact when d =0, so that the contact sufficiency is ensured, when a robot tool center point is in contact with the standard sphere, a contact signal is automatically detected, and the automatic control of a calibration process is realized.
2. A robot TCP calibration method using a floating standard ball according to any of claim 1, wherein said standard ball is a floatable standard ball, which is always at the same height without external force and only can move vertically up and down.
3. A robot TCP calibration method using a floating standard ball according to any one of claim 1, wherein it is determined whether the tool center point is in contact with the standard ball by the descending height of the floating standard ball.
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