CN112440269A - Robot arm length correction method and system - Google Patents
Robot arm length correction method and system Download PDFInfo
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- CN112440269A CN112440269A CN201910827925.6A CN201910827925A CN112440269A CN 112440269 A CN112440269 A CN 112440269A CN 201910827925 A CN201910827925 A CN 201910827925A CN 112440269 A CN112440269 A CN 112440269A
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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
- B25J9/02—Programme-controlled manipulators characterised by movement of the arms, e.g. cartesian coordinate type
- B25J9/023—Cartesian coordinate type
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J18/00—Arms
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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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Abstract
The invention provides a robot arm length correction method and system, wherein the method comprises the following steps: acquiring relative position data of a plurality of calibration points on a calibration plate relative to the same datum point; the robot drives the camera to move, and records a feedback rotation angle of the first motor and a feedback rotation angle of the second motor when the central point of the camera is superposed with each calibration point respectively; establishing an equation of the coordinates of each calibration point in a robot coordinate system and the length of the second arm, the length of the third arm, the feedback rotation angle of the first motor, the feedback rotation angle of the second motor, the length of the second arm, the length of the third arm, the deviation angle of the first motor and the deviation angle of the second motor; and solving the established equation according to the relative position data of each calibration point relative to the same reference point to obtain the length of the second arm, the length of the third arm, the deviation angle of the first motor and the deviation angle of the second motor. The invention realizes the unmanned automatic correction process, reduces the manufacturing cost and improves the correction success rate.
Description
Technical Field
The invention relates to the technical field of robot correction, in particular to a robot arm length correction method and system.
Background
With the rapid development of industrial automation, more and more robot applications are developing towards High precision (High accuracycacy), High efficiency (High efficiency), High stability (High stability) and Low cost (Low cost). In order to reduce the influence of part machining errors and assembly errors on the quality of the robot and improve the working precision, an arm length correction method before delivery is widely used in the robot manufacturing field.
The conventional arm length calibration methods in the industry generally include the following two methods: firstly, the method relies on a high-precision optical instrument to measure the size and the assembly linearity of a part, and then repeatedly adjust the size and the assembly linearity of the part until the error is controlled within a certain range, but the method greatly increases the manufacturing cost. Secondly, the robot is subjected to kinematic correction, errors of structural parameters of the robot are identified and algorithm compensation is carried out on the robot, so that the precision of the robot is improved.
Disclosure of Invention
The invention aims to provide a robot arm length correction method and system, which can realize unmanned automatic correction process, reduce manufacturing cost and improve correction success rate.
Additional features and advantages of the invention will be set forth in the detailed description which follows, or may be learned by practice of the invention.
According to a first aspect of the present invention, there is provided a robot arm length correction method, wherein arm length correction is performed on a robot to be corrected based on a calibration plate, the calibration plate is placed in parallel to a robot coordinate system, the robot comprises a first arm, a second arm and a third arm, the third arm is connected to the first arm through the second arm, the first arm is a fixed arm, the second arm is driven by a first motor to rotate relative to the first arm, the third arm is driven by a second motor to rotate relative to the second arm, and a camera is arranged at the tail end of the third arm;
the method comprises the following steps:
s100: acquiring relative position data of a plurality of calibration points on a calibration plate relative to the same datum point;
s200: the robot drives the camera to move, so that the camera captures images of the calibration points respectively, and a feedback rotation angle of the first motor and a feedback rotation angle of the second motor are recorded when a central point of the camera coincides with each calibration point respectively;
s300: establishing an equation of coordinates of the calibration point in the robot coordinate system and lengths of the second arm, the third arm, a feedback rotation angle of the first motor, a feedback rotation angle of the second motor, a length of the second arm, a length of the third arm, a deviation angle of the first motor and a deviation angle of the second motor for each calibration point of the calibration plate;
s400: and solving the equation established in the step S300 according to the relative position data of each calibration point relative to the same reference point to obtain the length of the second arm, the length of the third arm, the deviation angle of the first motor and the deviation angle of the second motor.
Optionally, in step S100, n calibration points on the calibration board are selected, the first calibration point is used as a reference point, and a coordinate value of the ith calibration point in the robot coordinate system is defined as (x)i，yi) Respectively acquiring the horizontal coordinate difference x of the ith calibration point relative to the reference pointi-x1And the difference y of the vertical coordinate of the ith calibration point relative to the reference pointi-y1，i∈(1，n)。
Optionally, in step S300, for each calibration point of the calibration board, the following equations (1) and (2) are established:
wherein, b2，b3Respectively the length of the second arm and the length of the third arm,
a feedback rotation angle of the first motor when the center point of the camera coincides with the ith calibration point,
a feedback rotation angle M of the second motor when the center point of the camera coincides with the ith calibration point1Is the deviation angle of the first motor, M2Is the deviation angle of the second motor.
Optionally, in step S100, four calibration points A, B, C, D on the calibration board are selected, a calibration point a is used as a reference point, coordinate values of the calibration point a in the robot coordinate system are defined as (x, y), and the abscissa differences a, c, e of the calibration point B, C, D with respect to the reference point and the ordinate differences b, d, f of the calibration point B, C, D with respect to the reference point are obtained respectively.
Optionally, in step S300, for each calibration point of the calibration board, the following equation is established:
wherein, b2，b3Respectively the length of the second arm and the length of the third arm,
the feedback rotation angle of the first motor when the center point of the camera coincides with the index point A, B, C, D,
the feedback rotation angle, M, of the second motor when the center point of the camera coincides with the index point A, B, C, D1Is the deviation angle of the first motor, M2Is the deviation angle of the second motor.
Optionally, a comparison image of a calibration object is stored in the camera, and the calibration point is a central point of the calibration object;
in step S200, the robot drives the camera to move, so that the camera captures images of the calibration points respectively, including the following steps:
the robot drives the camera to approach the calibration object;
the camera shoots an image of the calibration object, and the position of the calibration object is identified by adopting a stored comparison image of the calibration object;
the camera calculates the coordinate of the central point of the calibration object under a camera coordinate system according to the shape of the calibration object and sends the coordinate to the robot;
the robot drives the camera to move, so that the center point of the camera coincides with the center point of the calibration object.
Optionally, the camera coordinate system is parallel to the robot coordinate system, and the robot drives the camera to move, so that when the central point of the camera coincides with the central point of the calibration object, the robot drives the camera to move along the abscissa direction of the camera coordinate system and/or along the ordinate direction of the camera coordinate system.
Optionally, in step S100, four calibration points A, B, C, D are selected, the four calibration points form a rectangle, the calibration point A, B is parallel to the ordinate of the robot coordinate system, and the connecting line of the calibration point A, D is parallel to the abscissa of the robot coordinate system;
the robot drives the camera to move, so that when the central point of the camera coincides with the central point of the calibration object, the robot drives the camera to sequentially search the four calibration points A, B, C, D.
Optionally, after step S400, the method further includes the following steps:
inputting the length of the second arm, the length of the third arm, the deviation angle of the first motor, and the deviation angle of the second motor into a controller of the robot;
the controller of the robot takes the length of the second arm and the length of the third arm as the arm length of the robot, and determines actual control values of the first motor and the second motor based on the deviation angle of the first motor and the deviation angle of the second motor when controlling the first motor and the second motor.
The embodiment of the invention also provides a robot arm length correction system, which is applied to the robot arm length correction method, and the system comprises:
the data acquisition module is used for acquiring relative position data of a plurality of calibration points on the calibration plate relative to the same datum point;
the motor control module is used for controlling the first motor and the second motor so that the robot drives the camera to move, and the camera captures images of the calibration points respectively;
the data recording module is used for recording a feedback rotation angle of the first motor and a feedback rotation angle of the second motor when the central point of the camera is superposed with each calibration point respectively;
and the correction calculation module is used for establishing an equation of coordinate values of the calibration points in a robot coordinate system and the length of the second arm, the length of the third arm, the feedback rotation angle of the first motor, the feedback rotation angle of the second motor, the length of the second arm, the length of the third arm, the deviation angle of the first motor and the deviation angle of the second motor for each calibration point of the calibration plate, solving the equation according to the relative position data of each calibration point relative to the same reference point, and obtaining the length of the second arm, the length of the third arm, the deviation angle of the first motor and the deviation angle of the second motor.
The calibration plate and the camera are used for correcting the arm length of the robot and the deviation angle of the rotary driving motor, manual operation is not needed, the arm length of the robot is automatically and quickly corrected, errors possibly generated due to manual operation are reduced, the correction accuracy is improved, the correction efficiency is improved, and the production cost is reduced.
For a better understanding of the features and technical content of the present invention, reference should be made to the following detailed description of the present invention and accompanying drawings, which are included to illustrate and not limit the scope of the present invention.
Drawings
The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.
Fig. 1 is a schematic structural diagram of a robot to be calibrated according to an embodiment of the present invention;
FIG. 2 is a flow chart of a robot arm length correction method according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a calibration plate according to an embodiment of the present invention;
FIG. 4 is a schematic diagram illustrating the positions of four calibration points selected during arm length calibration of a robot according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of the calculation of arm length and offset angle according to an embodiment of the present invention;
FIG. 6 is a flow chart of a robot arm length correction method in accordance with an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a robot arm length correction system according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
In order to solve the technical problem in the prior art, the invention provides a robot arm length correction method, which is used for correcting the arm length of a robot to be corrected based on a calibration plate. As shown in fig. 1, the calibration plate 5 is placed parallel to a robot coordinate system, the robot includes a first arm 1, a second arm 2, and a third arm 3, the third arm 3 is connected to the first arm 1 through the second arm 2, the first arm 1 is a fixed arm, the second arm 2 is driven by a first motor to rotate relative to the first arm 1, the third arm 3 is driven by a second motor to rotate relative to the second arm 2, and a camera 4 is disposed at a distal end of the third arm 3. In this embodiment, the camera 4 is fixed to the end of the third arm 3 by a jig that is locked to the screw to keep the camera 4 horizontally positioned. The calibration plate 5 is placed against the block gauge 7 such that the calibration plate 5 is parallel to the robot coordinate system.
As shown in fig. 2, the robot arm length correction method includes the following steps:
s100: acquiring relative position data of a plurality of calibration points on a calibration plate relative to the same datum point;
s200: the robot drives the camera to move, so that the camera captures images of the calibration points respectively, and a feedback rotation angle of the first motor and a feedback rotation angle of the second motor are recorded when a central point of the camera coincides with each calibration point respectively;
s300: establishing an equation of coordinates of the calibration point in the robot coordinate system and lengths of the second arm, the third arm, a feedback rotation angle of the first motor, a feedback rotation angle of the second motor, a length of the second arm, a length of the third arm, a deviation angle of the first motor and a deviation angle of the second motor for each calibration point of the calibration plate;
s400: and solving the equation established in the step S300 according to the relative position data of each calibration point relative to the same reference point to obtain the length of the second arm, the length of the third arm, the deviation angle of the first motor and the deviation angle of the second motor.
Therefore, the calibration plate and the camera are used for correcting the arm length of the robot and the deviation angle of the rotary driving motor, manual operation is not needed, the arm length of the robot is automatically and quickly corrected, errors possibly caused by manual operation are reduced, the correction accuracy is improved, and the correction efficiency is improved.
In this embodiment, in step S100, n calibration points on the calibration board are selected, the first calibration point is used as a reference point, and the coordinate value of the ith calibration point in the robot coordinate system is defined as (x)i，yi) Respectively acquiring the horizontal coordinate difference x of the ith calibration point relative to the reference pointi-x1And the ith index point relative to the reference pointDifference y of ordinatei-y1，i∈(1，n)。
In this embodiment, in step S300, for each calibration point of the calibration board, the following equations (1) and (2) are established:
wherein, b2，b3Respectively the length of the second arm and the length of the third arm,
a feedback rotation angle of the first motor when the center point of the camera coincides with the ith calibration point,
a feedback rotation angle M of the second motor when the center point of the camera coincides with the ith calibration point1Is the deviation angle of the first motor, M2Is the deviation angle of the second motor.
In step S400, the coordinates of each calibration point are respectively substituted into the above equation (1) and equation (2), and the above equations are solved according to the positional relationship between each calibration point and the reference point, so as to obtain the length b of the second arm2Length b of the third arm3Deviation angle M of the first motor1And the deviation angle M of the second motor2。
In this embodiment, after step S400, the following steps are further included:
length b of the second arm2Length b of the third arm3Deviation angle M of the first motor1And the deviation angle M of the second motor2Inputting a controller of the robot;
the controller of the robot changes the length b of the second arm2And stationLength b of the third arm3As the arm length of the robot, and according to the deviation angle M of the first motor when controlling the first motor and the second motor1And the deviation angle M of said second motor2Actual control values for the first and second motors are determined. For example, when the first motor needs to be controlled to rotate by a predetermined angle, the deviation angle M of the first motor is taken into consideration1When a control command is sent to the first motor, the specified angle is determined according to the deviation angle M1Increase or decrease.
A method for correcting the length of the robot arm according to an embodiment of the present invention will be described with reference to fig. 3 to 6. It is understood that the specific embodiments are only for the purpose of more clearly illustrating the technical solutions of the present invention, and are not to be taken as limiting the scope of the present invention.
As shown in fig. 3, the structure of the calibration board in this embodiment is shown. The calibration plate 5 has a plurality of outer circles 51 and a plurality of inner circles 52, and the outer circles 51 and the inner circles 52 may be the same or different in size. The size of the calibration plate 5, the diameter of the outer circle 51 and the diameter of the inner circle 52 can be selected as desired. The calibration plate 5 can be made of glass, and the circular marking points and the grid lines are printed on the glass in a photomask (etching) mode.
As shown in fig. 4, in this embodiment, in step S100, four calibration points A, B, C, D on the calibration board are selected as calibration points to be used in the correction. Taking the calibration point A as a reference point, and defining the coordinate value of the calibration point A under the robot coordinate system as P1(x, y) obtaining lateral coordinate differences a, c, e of index point B, C, D and vertical coordinate differences b, d, f of index point B, C, D relative to the reference point, respectively. Thus, the coordinate of the index point B is P2(x + a, y + b), and the coordinate of the index point C is P2(x + c, y + D) and the coordinate of the index point D is P2(x+e，y+f)。
As shown in fig. 5, a schematic diagram of the equation established in step S300 is shown. For the coordinates of each point with respect to the robot coordinate system, the arm length of the second arm, the arm length of the third arm, the actual rotation angle of the first motor, and the actual rotation angle of the second motor may be used for calculation. The actual rotation angle of the first motor is related to the feedback rotation angle of the first motor and the deviation angle of the first motor, and the actual rotation angle of the second motor is related to the feedback rotation angle of the second motor and the deviation angle of the second motor.
As shown in fig. 5, θ1，θ2Using motor feedback position, b2，b3Is the arm length.
Wherein theta is1＝θt1+M1，θ2＝θt2+M2
θ1，θ2The first motor feedback rotation angle and the second motor feedback rotation angle are actual measurement angles respectively obtained by an encoder of the motor. Thetat1，θt2The actual rotation angle in this posture is derived from inverse kinematics, i.e. the actual rotation angle of the first motor and the actual rotation angle of the second motor. M1，M2The motor deviation angle is a value to be solved for correction.
The feedback rotation angle of the first motor can be determined according to a feedback PUU (subscriber unit pulse) value of the first motor, and the feedback rotation angle of the second motor can be determined according to a feedback PUU value of the second motor.
Fig. 6 is a specific flowchart of the robot arm length correction in this embodiment. First, corresponding to step S100, the user inputs the required parameters: positional relationship data of the index points (including positional data of the respective index points with respect to the reference standard points, as in this embodiment, d shown in fig. 4 is input1And d2According to d1And d2The horizontal coordinate differences a, c, e of the calibration point B, C, D and the vertical coordinate differences b, d, f of the calibration point B, C, D with respect to the reference point, the camera resolution center point, the camera error-tolerant pixel value (X, Y) (e.g., set to 1 pixel, but the invention is not limited thereto) and the output coordinate value of the camera. The motor parameters, including the reduction ratios and electronic gear ratios of the first and second motors are then read. Then the machineThe person establishes communication with the camera, sets related communication parameters, which may include communication transmission rate, and sets the camera as a master station and the robot as a slave station, so that the camera actively transmits coordinate data to the robot during calibration.
In this embodiment, the four index points A, B, C, D form a rectangle, index point A, B is parallel to the ordinate of the robot coordinate system, and the line connecting index points A, D is parallel to the abscissa of the robot coordinate system.
Corresponding to step S200, in the calibration process, when the camera is controlled to move, because the camera captures several images at the same location, and the values are different, the robot arm performs inching in a coarse tuning and fine tuning manner, where the coarse tuning is to reduce the calibration time, but the precision of the robot arm is not sufficient before calibration, and the fine tuning inching must be used to reach the mark point position. In this embodiment, the camera is first moved to a position near the first point a in the coarse inching mode, the C-axis (the rotation axis at the end of the third arm) is fixed at zero, and the relationship between the camera and the coordinates of the mechanical arm is automatically found. Then, the four calibration points are automatically searched, the center point of the camera is aligned to the center of each marker point by utilizing the fine tuning movement, the motor feedback values of the four points are recorded, namely the feedback PUU of the first motor and the feedback PUU of the second motor at each calibration point in the four calibration points, and the feedback rotation angle of the first motor and the feedback rotation angle of the second motor are calculated according to the feedback PUU of the first motor and the feedback PUU of the second motor.
In this embodiment, a comparison image of a calibration object is stored in the camera, and the calibration point is a central point of the calibration object. In step S200, the robot drives the camera to move, so that the camera captures images of the calibration points respectively, including the following steps:
the robot drives the camera to approach the calibration object;
the camera shoots an image of the calibration object, and the position of the calibration object is identified by adopting a stored comparison image of the calibration object;
the camera calculates the coordinate of the central point of the calibration object under a camera coordinate system according to the shape of the calibration object and sends the coordinate to the robot;
the robot drives the camera to move, so that the center point of the camera coincides with the center point of the calibration object.
In this embodiment, since the camera coordinate system is parallel to the robot coordinate system, the calibration point A, B is parallel to the ordinate of the robot coordinate system, the connecting line of the calibration point A, D is parallel to the abscissa of the robot coordinate system, and the robot drives the camera to move, so that when the central point of the camera coincides with the central point of the calibration object, the robot drives the camera to move along the abscissa of the camera coordinate system and/or along the ordinate of the camera coordinate system.
Further, the robot drives the camera to sequentially search for the four calibration points A, B, C, D. Specifically, the method comprises the following steps:
(1) the center point of the camera moved by the robot arm is coincident with the calibration point A, and the feedback rotation angle of the first motor at the moment is recorded
And the second motor feedback rotation angle
(2) The robot arm moves to the center point of the camera and coincides with the calibration point B, the distance from A → B in the X direction a and the distance from Y direction B are recorded, and the feedback rotation angle of the first motor at the time is recorded
And the second motor feedback rotation angle
(3) The robot arm moves to the center point of the camera and coincides with the calibration point C, the distance from B → C in the X direction C and the distance from Y direction d are recorded, and the feedback rotation angle of the first motor at the moment is recorded
And the second motor feedback rotation angle
(4) The robot arm moves to the center point of the camera and coincides with the calibration point D, the distance from C → D in the X direction e and the distance from C → D in the Y direction f are recorded, and the feedback rotation angle of the first motor at the time is recorded
And the second motor feedback rotation angle
At this time, the known information is a, b, c, d, e, f moving distance information, and the value of the rotation angle of the feedback amount of the motor:
in this embodiment, in step S300, the following equation is established for each calibration point of the calibration plate. Specifically, the following equation is established for the calibration point a:
the following equation is established for calibration point B:
the following equation is established for the index point C:
the following equation is established for the calibration point D:
wherein, b2，b3Respectively the length of the second arm and the length of the third arm,
the feedback rotation angle of the first motor when the center point of the camera coincides with the index point A, B, C, D,
the feedback rotation angle, M, of the second motor when the center point of the camera coincides with the index point A, B, C, D1Is the deviation angle of the first motor, M2Is the deviation angle of the second motor.
Corresponding to step S400, the positional relationship data a, b, c, d, e, f of the four calibration points A, B, C, D, the feedback rotation angle of the first motor are calculated
Feedback rotation angle of second motor
Substituted into each of the above-established etcIn the formula, the length b of the second arm and the third arm is calculated and obtained2，b3Deviation angle M of the first motor1And the deviation angle M of the second motor2The value of (c).
The specific calculation process is as follows:
developing x, y for each of the above equations yields the following equation:
sorting out known items, and solving the lengths b of the second arm and the third arm in a matrix representation2，b3Deviation angle M of the first motor1And the deviation angle M of the second motor2The value of (c):
and B is A.X, and X is solved.
Solving by using a least square solution (optimal solution), and solving for M by using an arctangent function relation1，M2Then find b2，b3：
Then, the lengths b of the second and third arms are adjusted2，b3Deviation angle M of the first motor1And the deviation angle M of the second motor2The value of (2) is written into a controller of the robot, and arm length correction of the robot is completed.
Specifically, after the parameters are written into a controller of the robot, the corrected parameters are used as new arm length and motor rotation parameters to participate in forward and reverse kinematics.
The formula for the forward kinematics is as follows:
Px＝wc124+b3c12+b2c1
Py＝ws124+b3s12+b2s1
Pz＝q3-h
note that:
c124＝cos(θ1+θ2+θ4+M1+M2)
s124＝sin(θ1+θ2+θ4+M1+M2)
c12＝cos(θ1+θ2+M1+M2)
s12＝sin(θ1+θ2+M1+M2)
c1＝cos(θ1+M1)
s1＝sin(θ1+M1)
reverse kinematics:
q3＝-P4z
θ2＝tan-1(N，D)
θ4＝θ124-θ1-θ2
θ1＝θ1+M1
θ2＝θ2+M2
Length b of the second arm and the third arm2，b3Deviation angle M of the first motor1And the deviation angle M of the second motor2Substituting the value of (a) into the forward kinematic formula and the reverse kinematic formula.
As shown in fig. 7, an embodiment of the present invention further provides a robot arm length correction system, which is applied to the robot arm length correction method, and the system includes:
the data acquisition module M100 is used for acquiring relative position data of a plurality of calibration points on the calibration plate relative to the same reference point;
a motor control module M200, configured to control the first motor and the second motor, so that the robot drives the camera to move, and the camera captures images of the calibration points respectively;
a data recording module M300, configured to record a feedback rotation angle of the first motor and a feedback rotation angle of the second motor when a center point of the camera coincides with each of the calibration points, respectively;
and the correction calculation module M400 is configured to, for each calibration point of the calibration plate, establish an equation between coordinate values of the calibration point in the robot coordinate system and a length of the second arm, a length of the third arm, a feedback rotation angle of the first motor, a feedback rotation angle of the second motor, a length of the second arm, a length of the third arm, a deviation angle of the first motor, and a deviation angle of the second motor, and solve the equation according to relative position data of each calibration point with respect to the same reference point to obtain a length of the second arm, a length of the third arm, a deviation angle of the first motor, and a deviation angle of the second motor.
In the robot arm length correction system of the present invention, the functions of the respective modules may be implemented by using the specific embodiments of the above steps, for example, the function of the data acquisition module M100 may be implemented by using the specific embodiment of the step S100, the functions of the motor control module M200 and the data recording module M300 may be implemented by using the specific embodiment of the step S200, and the function of the correction calculation module M400 may be implemented by using the specific embodiments of the step S300 and the step S400. And will not be described in detail herein.
In summary, compared with the prior art, the calibration plate and the camera are used for correcting the arm length of the robot and the deviation angle of the rotary driving motor, manual operation is not needed, the arm length of the robot is automatically and quickly corrected, errors possibly generated due to manual operation are reduced, the correction accuracy rate is improved, the correction efficiency is improved, and the production cost is reduced.
The present invention has been described in relation to the above embodiments, which are only exemplary of the implementation of the present invention. It should be noted that the disclosed embodiments do not limit the scope of the invention. Rather, it is intended that all such modifications and variations be included within the spirit and scope of this invention.
Claims (10)
1. The robot arm length correction method is characterized in that arm length correction is carried out on a robot to be corrected based on a calibration plate, the calibration plate is placed in parallel to a robot coordinate system, the robot comprises a first arm, a second arm and a third arm, the third arm is connected to the first arm through the second arm, the first arm is a fixed arm, the second arm is driven by a first motor to rotate relative to the first arm, the third arm is driven by a second motor to rotate relative to the second arm, and a camera is arranged at the tail end of the third arm;
the method comprises the following steps:
s100: acquiring relative position data of a plurality of calibration points on a calibration plate relative to the same datum point;
s200: the robot drives the camera to move, so that the camera captures images of the calibration points respectively, and a feedback rotation angle of the first motor and a feedback rotation angle of the second motor are recorded when a central point of the camera coincides with each calibration point respectively;
s300: establishing an equation of coordinates of the calibration point in the robot coordinate system and lengths of the second arm, the third arm, a feedback rotation angle of the first motor, a feedback rotation angle of the second motor, a length of the second arm, a length of the third arm, a deviation angle of the first motor and a deviation angle of the second motor for each calibration point of the calibration plate;
s400: and solving the equation established in the step S300 according to the relative position data of each calibration point relative to the same reference point to obtain the length of the second arm, the length of the third arm, the deviation angle of the first motor and the deviation angle of the second motor.
2. A robot arm length correction method according to claim 1, wherein in step S100, n calibration points on a calibration plate are selected, a first calibration point is used as a reference point, and coordinate values of an i-th calibration point in the robot coordinate system are defined as (x) coordinate valuesi，yi) Respectively acquiring the horizontal coordinate difference x of the ith calibration point relative to the reference pointi-x1And the difference y of the vertical coordinate of the ith calibration point relative to the reference pointi-y1,i∈(1，n)。
3. The robot arm length correction method according to claim 2, wherein in step S300, for each calibration point of the calibration plate, the following equations (1) and (2) are established:
wherein, b2，b3Respectively the length of the second arm and the length of the third arm,
a feedback rotation angle of the first motor when the center point of the camera coincides with the ith calibration point,
a feedback rotation angle M of the second motor when the center point of the camera coincides with the ith calibration point1Is the deviation angle of the first motor, M2Is the deviation angle of the second motor.
4. The robot arm length correction method according to claim 1, wherein in step S100, four calibration points A, B, C, D on a calibration plate are selected, a calibration point a is defined as a reference point, and coordinate values of the calibration point a in the robot coordinate system are defined as (x, y), and lateral coordinate differences a, c, e of a calibration point B, C, D with respect to the reference point and vertical coordinate differences b, d, f of a calibration point B, C, D with respect to the reference point are obtained, respectively.
5. The method of correcting a robot arm length according to claim 4, wherein in step S300, for each calibration point of the calibration plate, the following equation is established:
wherein, b2，b3Respectively the length of the second arm and the length of the third arm,
the feedback rotation angle of the first motor when the center point of the camera coincides with the index point A, B, C, D,
the feedback rotation angle, M, of the second motor when the center point of the camera coincides with the index point A, B, C, D1Is the deviation angle of the first motor, M2Is the deviation angle of the second motor.
6. The method of robot arm length correction according to claim 1, wherein a comparison image of a calibration object is stored in the camera, and the calibration point is a center point of the calibration object;
in step S200, the robot drives the camera to move, so that the camera captures images of the calibration points respectively, including the following steps:
the robot drives the camera to approach the calibration object;
the camera shoots an image of the calibration object, and the position of the calibration object is identified by adopting a stored comparison image of the calibration object;
the camera calculates the coordinate of the central point of the calibration object under a camera coordinate system according to the shape of the calibration object and sends the coordinate to the robot;
the robot drives the camera to move, so that the center point of the camera coincides with the center point of the calibration object.
7. The method of robot arm length correction according to claim 6, wherein the camera coordinate system is parallel to the robot coordinate system, and wherein the moving the camera by the robot such that the center point of the camera coincides with the center point of the calibration object comprises moving the camera by the robot in a direction along an abscissa of the camera coordinate system and/or in a direction along an ordinate of the camera coordinate system.
8. The robot arm length correction method according to claim 7, wherein in step S100, four calibration points A, B, C, D are selected, the four calibration points forming a rectangle, the calibration point A, B being parallel to the ordinate of the robot coordinate system, the connecting line of the calibration points A, D being parallel to the abscissa of the robot coordinate system;
the robot drives the camera to move, so that when the central point of the camera coincides with the central point of the calibration object, the robot drives the camera to sequentially search the four calibration points A, B, C, D.
9. The method of correcting a robot arm length according to claim 1, further comprising, after the step S400, the steps of:
inputting the length of the second arm, the length of the third arm, the deviation angle of the first motor, and the deviation angle of the second motor into a controller of the robot;
the controller of the robot takes the length of the second arm and the length of the third arm as the arm length of the robot, and determines actual control values of the first motor and the second motor based on the deviation angle of the first motor and the deviation angle of the second motor when controlling the first motor and the second motor.
10. A robot arm length correction system to be applied to the robot arm length correction method according to any one of claims 1 to 9, the system comprising:
the data acquisition module is used for acquiring relative position data of a plurality of calibration points on the calibration plate relative to the same datum point;
the motor control module is used for controlling the first motor and the second motor so that the robot drives the camera to move, and the camera captures images of the calibration points respectively;
the data recording module is used for recording a feedback rotation angle of the first motor and a feedback rotation angle of the second motor when the central point of the camera is superposed with each calibration point respectively;
and the correction calculation module is used for establishing an equation of coordinate values of the calibration points in a robot coordinate system and the length of the second arm, the length of the third arm, the feedback rotation angle of the first motor, the feedback rotation angle of the second motor, the length of the second arm, the length of the third arm, the deviation angle of the first motor and the deviation angle of the second motor for each calibration point of the calibration plate, solving the equation according to the relative position data of each calibration point relative to the same reference point, and obtaining the length of the second arm, the length of the third arm, the deviation angle of the first motor and the deviation angle of the second motor.
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