CN110695993B - Synchronous measurement method, system and device for flexible mechanical arm - Google Patents

Synchronous measurement method, system and device for flexible mechanical arm Download PDF

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CN110695993B
CN110695993B CN201910925143.6A CN201910925143A CN110695993B CN 110695993 B CN110695993 B CN 110695993B CN 201910925143 A CN201910925143 A CN 201910925143A CN 110695993 B CN110695993 B CN 110695993B
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mechanical arm
flexible mechanical
tail end
coordinate system
pose
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CN110695993A (en
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徐文福
彭键清
严盼辉
梁斌
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Shenzhen Graduate School Harbin Institute of Technology
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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
    • B25J9/1615—Programme controls characterised by special kind of manipulator, e.g. planar, scara, gantry, cantilever, space, closed chain, passive/active joints and tendon driven manipulators
    • 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
    • B25J19/0095—Means or methods for testing manipulators
    • 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
    • B25J19/02—Sensing devices
    • B25J19/04—Viewing devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • 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
    • B25J9/1602—Programme controls characterised by the control system, structure, architecture
    • B25J9/1605—Simulation of manipulator lay-out, design, modelling of manipulator
    • 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
    • B25J9/1602—Programme controls characterised by the control system, structure, architecture
    • B25J9/161—Hardware, e.g. neural networks, fuzzy logic, interfaces, processor

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  • Robotics (AREA)
  • Mechanical Engineering (AREA)
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  • Length Measuring Devices By Optical Means (AREA)

Abstract

The invention discloses a synchronous measurement method of a flexible mechanical arm and a synchronous measurement system of the flexible mechanical arm with the synchronous measurement method, wherein the synchronous measurement method of the flexible mechanical arm comprises the following steps: acquiring typical characteristic information of the flexible mechanical arm; converting a coordinate system to obtain the relative pose relationship among the base, the rotation center of each joint and the tail end of the flexible mechanical arm; acquiring pose information of each rotary joint and the tail end of the flexible mechanical arm and relative to the hand-eye camera and the mobile base through the relative pose relationship; and establishing a flexible mechanical arm motion model according to the pose information so as to quickly acquire typical characteristic information of the flexible mechanical arm, carrying out coordinate transformation, further accurately acquiring pose information of each rotating joint and the tail end of the flexible mechanical arm, and accurately establishing the flexible mechanical arm motion model. The synchronous measurement method, the system and the device of the flexible mechanical arm can accurately establish the motion model of the flexible mechanical arm and carry out precision measurement.

Description

Synchronous measurement method, system and device for flexible mechanical arm
Technical Field
The invention relates to the field of vision measurement, in particular to a synchronous measurement method, system and device for a flexible mechanical arm.
Background
With the rapid development of scientific technology, the autonomous operation of the intelligent robot technology in the aspects of unstructured environments such as aerospace, nuclear power stations, narrow pipelines and emergency rescue and relief work becomes more and more important, and how to effectively sense the environment and autonomously complete specified tasks in the operating environment of dangerous unstructured extremes and narrow pipelines has a very important meaning.
In a limited narrow environment, the traditional mechanical arm is not suitable for an unstructured working environment due to low flexibility, and the flexible mechanical arm has the advantages of super-redundancy degree of freedom, flexible structure and small motion load, and is suitable for occasions requiring the robot to have flexible sensing capacity. However, the flexible mechanical arm realizes bending through the tensile force of the rope, but factors influencing the motion precision of the flexible mechanical arm and a multi-level coupling mechanism are not clear, so that the flexible mechanical arm generally has the problems of difficult modeling, poor motion precision and the like.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a synchronous measurement method of a flexible mechanical arm, which can acquire pose information of each rotary joint and the tail end of the flexible mechanical arm through typical characteristic information of the flexible mechanical arm and carry out coordinate transformation to establish a flexible mechanical arm motion model.
The invention also provides a synchronous measuring device with the synchronous measuring method of the flexible mechanical arm.
According to the embodiment of the first aspect of the invention, the synchronous measurement method of the flexible mechanical arm comprises the following steps:
acquiring typical characteristic information of the flexible mechanical arm;
converting a coordinate system to obtain the relative pose relationship among the base, the rotation center of each joint and the tail end of the flexible mechanical arm;
acquiring pose information of each rotary joint and the tail end of the flexible mechanical arm relative to the base through the relative pose relation;
and establishing a flexible mechanical arm motion model according to the pose information.
The synchronous measurement method of the flexible mechanical arm provided by the embodiment of the invention at least has the following beneficial effects: the method comprises the steps of rapidly obtaining typical characteristic information of the flexible mechanical arm, carrying out coordinate transformation, accurately obtaining pose information of each rotating joint and the tail end of the flexible mechanical arm, and accurately establishing a flexible mechanical arm motion model.
According to an embodiment of the invention, the typical characteristic information is obtained by shooting two-dimensional codes on each joint component and the tail end of the flexible mechanical arm. The relative pose relationship among the base, the rotation center of each joint and the tail end of the flexible mechanical arm can be quickly obtained by arranging the two-dimensional codes with typical characteristic information on the surfaces of the joint components and the tail end.
According to the further embodiment of the invention, the relative pose relationship is obtained according to the typical feature information and the pose transformation relationship from the two-dimensional code coordinate system to the camera coordinate system.
According to another embodiment of the present invention, the relative pose relationship between the rotation center of the joint member and the two-dimensional code center is combined according to the typical feature information to obtain the pose relationship of each rotation center in the camera coordinate system, so as to obtain the corresponding joint angle. Through the position and posture relation of each rotation center in a camera coordinate system, each joint angle is accurately solved, and the error of the motion model of the whole flexible mechanical arm can be reduced.
According to the further embodiment of the invention, the starting state and the specific arm type of the flexible mechanical arm are reset and calibrated through the joint angle, so that a motion model and a model calibration are established for the flexible mechanical arm. The initial state of the flexible mechanical arm and the specific arm type are obtained through the joint angle for resetting and calibrating, the established motion model is more accurate, and errors between the motion model and the actual arm type of the motion model can be reduced by carrying out secondary calibration on the motion model.
According to another embodiment of the invention, the pose information of the target to be measured in the camera coordinate system is measured by the hand-eye camera, and the pose information of the tail end of the flexible mechanical arm in the base coordinate system is combined to perform hand-eye calibration, so as to obtain the pose relationship of the target to be measured in the base coordinate system. By using the hand-eye camera to perform hand-eye determination on the target to be detected, the pose relation of the target to be detected in the base coordinate system can be obtained.
According to the embodiment of the second aspect of the invention, the flexible mechanical arm synchronous measuring device comprises:
the characteristic extraction module is used for executing the steps to obtain typical characteristic information of each joint section and the tail end of the flexible mechanical arm;
the calibration conversion module is used for executing the steps and respectively acquiring the relative pose relations of the base, the rotation centers of the joints and the tail end of the flexible mechanical arm through coordinate system conversion;
the synchronous reconstruction module is used for obtaining pose information of each rotating joint and the tail end of the flexible mechanical arm relative to the base through kinematic recursion in the execution step;
and the precision evaluation module is used for evaluating the shape and the tail end positioning precision of the flexible mechanical arm by executing steps.
The synchronous measuring device of the flexible mechanical arm provided by the embodiment of the invention at least has the following beneficial effects: the method comprises the steps of rapidly obtaining typical characteristic information of the flexible mechanical arm, carrying out coordinate transformation to accurately obtain pose information of each rotating joint and the tail end of the flexible mechanical arm, accurately establishing a flexible mechanical arm motion model, and evaluating positioning accuracy.
According to the third aspect embodiment of the invention, the flexible mechanical arm synchronous measuring device comprises: the system comprises a flexible mechanical arm, a task board, a mobile base, a first global camera, a second global camera and a microprocessor;
the flexible mechanical arm is arranged on the movable base;
the flexible mechanical arm is provided with a plurality of rotating joints and a mechanical arm tail end device, and two-dimensional codes are arranged on the rotating joints and the mechanical arm tail end device;
the tail end of the flexible mechanical arm is provided with a hand-eye camera, and the hand-eye camera is used for measuring pose information of the target to be measured in a camera coordinate system;
the first global camera and the second global camera are arranged on one side of the mobile base and used for shooting the two-dimensional code to obtain typical feature information;
and the task board is used for calibrating the parameters of the hand-eye camera.
The synchronous measuring device of the flexible mechanical arm provided by the embodiment of the invention at least has the following beneficial effects: the method comprises the steps of rapidly obtaining typical characteristic information of the flexible mechanical arm, carrying out coordinate transformation to accurately obtain pose information of each rotating joint and the tail end of the flexible mechanical arm, accurately establishing a flexible mechanical arm motion model, and evaluating positioning accuracy. And the parameters of the hand-eye camera can be calibrated, and the synchronous measurement device of the flexible mechanical arm can perform synchronous displacement in the measurement process by moving the base.
According to another embodiment of the invention, a plurality of calibration areas are arranged on the task board, and the calibration areas comprise a target ball disc area, a calibration board area, a two-dimensional code area, a mark point area, a slit area, a round hole area and a rectangular area. The shape of the flexible mechanical arm and the measurement precision of the tail end are evaluated by arranging a target ball disc area and externally arranging a laser tracker; and calibrating by using parameters of the hand-eye camera by setting a calibration plate area.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a three-dimensional schematic view of a flexible robot vision measuring system according to a first embodiment of the present invention;
FIG. 2 is a flow chart of a method for synchronous measurement of a flexible robotic arm according to the present invention;
FIG. 3 is a three-dimensional schematic view of a vision measurement task board according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a relative relationship between a laser tracker, a camera, and a two-dimensional code according to an embodiment of the method for synchronously measuring a flexible robot arm of the present invention;
FIG. 5 is a schematic diagram of interpolation solution of the rotation center of a synchronous measurement method of a flexible manipulator according to an embodiment of the present invention
FIG. 6 is a schematic diagram of relative poses of a joint rotation center and a two-dimensional code center coordinate system according to an embodiment of the synchronous measurement method for the flexible manipulator;
FIG. 7 is a D-H coordinate system distribution diagram of a flexible robot according to an embodiment of the present invention;
FIG. 8 is a diagram of a distribution relationship of D-H coordinate systems of a flexible manipulator according to a synchronous measurement method of the flexible manipulator.
Description of reference numerals: 1. a flexible mechanical arm; 2. a task board; 3. a movable base; 4. a first global camera; 5. a second global camera; 6. a hand-eye camera.
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 accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
Example one
The embodiment of the invention provides a synchronous measuring device for a flexible mechanical arm, and is suitable for the field of synchronous measurement of the shape and the tail end pose of the flexible mechanical arm needing to be controlled.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a synchronous measurement device of a flexible robot arm according to an embodiment of the present invention. As shown in fig. 1, the synchronous measuring apparatus of the flexible robot arm 1 includes: the system comprises a flexible mechanical arm 1, a task board 2, a mobile base 3, a first global camera 4, a second global camera 5 and a microprocessor (not shown); the flexible mechanical arm 1 is arranged on the moving base 3; the flexible mechanical arm 1 is provided with a plurality of rotating joints and a mechanical arm tail end device, and two-dimensional codes are arranged on the surfaces of the rotating joints and the mechanical arm tail end device; the tail end of the flexible mechanical arm 1 is provided with a hand-eye camera 6, and the hand-eye camera 6 is used for measuring pose information of the target to be measured in a camera coordinate system; the first global camera 4 and the second global camera are arranged on one side of the mobile base 3 and used for shooting the two-dimensional code to obtain typical feature information; and the task board 2 is used for calibrating the parameters of the hand-eye camera 6. And the microprocessor is used for processing the typical characteristic information and converting a coordinate system to acquire the relative pose relationship among the moving base, the rotating centers of the joints and the tail end of the flexible mechanical arm, and further acquiring pose information according to the relative pose relationship. The microprocessor can establish a flexible mechanical arm motion model according to the pose information.
Wherein the moving base 3 can be provided with a moving trolley. The task board 2 is provided with a plurality of calibration areas, and the calibration areas comprise a target ball disc area, a calibration board area, a two-dimensional code area, a mark point area, a slit area, a round hole area and a rectangular area.
The calibration plate area is used for accurately calibrating the internal parameters and the external parameters of the hand-eye camera and the global camera; the two-dimensional code area and the mark point area are used for calculating pose information of the tail end of the flexible mechanical arm; the slit area, the circular hole area and the rectangular area are used for simulating and expanding the synchronous measuring device.
In addition, a laser tracker can be additionally arranged, and the relative pose information of the target ball disc area and the calibration plate area can be calibrated through the laser tracker.
Example two
The embodiment of the invention provides a synchronous measurement system of a flexible mechanical arm, which is suitable for the field of synchronous measurement of the shape and the tail end pose of the flexible mechanical arm needing to be controlled. The synchronous measurement system comprises a feature extraction module, a calibration conversion module, a synchronous reconstruction module and a precision evaluation module.
The characteristic extraction module is used for executing the steps to obtain typical characteristic information of each joint section and the tail end of the flexible mechanical arm;
the calibration conversion module is used for executing the steps and respectively acquiring the relative pose relations of the base, the rotation centers of the joints and the tail end of the flexible mechanical arm through coordinate system conversion;
the synchronous reconstruction module is used for obtaining pose information of each rotating joint and the tail end of the flexible mechanical arm relative to the base through kinematic recursion in the execution step;
and the precision evaluation module is used for evaluating the shape and the tail end positioning precision of the flexible mechanical arm by executing steps.
And the tail end of the flexible mechanical arm is provided with a hand-eye camera so as to measure pose information of the target to be measured under a camera coordinate system.
EXAMPLE III
The third embodiment of the invention provides a synchronous measurement method of a flexible mechanical arm, which is suitable for the field of synchronous measurement of the shape and the tail end pose of the flexible mechanical arm needing to be controlled.
Referring to fig. 1 and fig. 3, fig. 3 is a flowchart illustrating an implementation of a synchronous measurement method for a flexible robot arm according to an embodiment of the present invention. The third embodiment is described in detail with reference to the first embodiment, and the method mainly includes the following steps:
s1: acquiring typical characteristic information of the flexible mechanical arm;
s2: obtaining the relative pose relationship among the base, the rotation centers of all joints and the tail end of the flexible mechanical arm through coordinate system conversion;
s3: acquiring pose information of each rotary joint and the tail end of the flexible mechanical arm relative to the moving base through the relative pose relation;
s4: and establishing a flexible mechanical arm motion model according to the pose information.
In step S1, the two-dimensional code arranged on the surface of the turning joint and the end device of the flexible mechanical arm 1 may be photographed by the first global camera 4 and the second global camera 5 to obtain typical characteristic information of the flexible mechanical arm 1. The pose information of the flexible mechanical arm 1 can be obtained by establishing a camera coordinate system of the first global camera 4 and the second global camera 5 and combining the typical characteristic information of the flexible mechanical arm 1.
In step S2, since the relative positional relationship between the rotation center of the rotational joint and the two-dimensional code is known, the relative positional relationship between the rotation centers in the camera coordinate system can be obtained, and the corresponding joint angle can be obtained.
In step S3, the relative positional relationship found in step S2 and the relative positional relationship of the moving base 3 are combined to obtain the positional relationship of the entire synchronous measuring device.
In step S4, a motion model is built according to the above pose relationship to obtain the motion state of the entire flexible mechanical arm 1 synchronous measurement device in real time.
The synchronous measurement method of the flexible mechanical arm 1 may further include step S4: and setting a task board 2 to calibrate the internal reference and the external reference of the camera and evaluate the measurement precision.
In the step S1, the pose information of the flexible mechanical arm 1 is acquired, and the task board 2 is provided with a calibration board area, so that the internal reference and the external reference can be calibrated through the calibration board area and the measurement accuracy can be evaluated.
In addition, a target ball disc area is arranged in the task board 2, the area and the calibration board area are calibrated by additionally arranging a laser tracker, and relative pose information of the area and the calibration board area is obtained.
The tail end of the flexible mechanical arm 1 is further provided with a hand-eye camera 6, the pose information of the target to be detected under a hand-eye camera coordinate system can be measured in real time through the hand-eye camera 6, and the pose information of the target to be detected under the base coordinate system is obtained by combining the pose information of the tail end of the flexible mechanical arm 1 under the base coordinate system, which is detected by the first global camera 4 and the second global camera 5, so that the pose information of the target to be detected under the base coordinate system is obtained.
And a two-dimensional code area and a mark point area are also arranged in the task board 2 and are used for being matched with the additionally arranged laser tracker so as to evaluate the precision of a measurement algorithm. By arranging the slit region, the circular hole region and the rectangular region in the task board 2 and presetting the relative pose relationship of each region in the task board 2, the tasks required by the synchronous measuring device of the flexible mechanical arm 1 can be simulated and expanded through the task board 2.
Because each rotary joint of the flexible mechanical arm 1 is provided with a two-dimensional code with a unique pattern. The two-dimensional code is identified by the first global camera 4 and the second global camera 5, so that the typical characteristic information corresponding to the two-dimensional code can be obtained, namely the shape and the terminal pose information of the flexible mechanical arm 1 are measured by using the discretely distributed two-dimensional code and matching with a multi-point measuring system. And a laser tracker is additionally arranged to measure the shape and the tail end pose information of the flexible mechanical arm 1, and the pose information obtained by measuring the multipoint measuring system and the laser tracker is compared to evaluate the measuring precision of the shape and the tail end of the flexible mechanical arm 1.
The joint angle of each rotating joint can be indirectly obtained by measuring the shape and the tail end of the flexible mechanical arm 1, so that the joints are controlled and adjusted, and meanwhile, the convenience of expansion and use of a task space is realized by means of integrated compact movable platform design.
Practice four
Referring to fig. 4, fig. 4 is a three-dimensional schematic view of a vision measurement task board of a flexible robot attitude synchronization measurement method according to an embodiment of the present invention. As shown in fig. 4, the task board 2 includes a plurality of calibration areas, including a drone plate area 201, a calibration board area 202, a two-dimensional code area 203, a marker point area 204, a rectangular slit area 205, a circular hole area 206, and a charging area 207.
The calibration board area is provided with a chessboard distribution pattern for accurately calibrating the internal parameters and the external parameters of the hand-eye camera and the global camera; a visual positioning two-dimensional code such as an Apritag two-dimensional code is arranged in the two-dimensional code area; the target ball disk area is provided with a plurality of target balls suitable for visual tracking. The charging area 207 is used for charging the flexible mechanical arm, and can be provided as an aviation charging plug.
Example 5
Referring to fig. 5, fig. 5 is a schematic diagram illustrating component positions of a flexible robot arm synchronous measurement method according to an embodiment of the present invention. The relative positional relationship between the laser tracker 7, the hand-eye camera 6, and the two-dimensional code region 203 will be described below with reference to fig. 5.
The relative pose relationship between the target ball disc area 201 and the calibration plate area 202 is fixed, the target ball disc area 201 and the calibration plate area 202 with the relative pose fixed are calibrated through the laser tracker 7, and the relative pose information between a laser tracker coordinate system and a camera coordinate system can be calculated. To evaluate the positioning accuracy of the visual positioning two-dimensional code in the two-dimensional code region 203. The specific process of precision evaluation is expanded as follows:
the laser tracker 7 can be used for measuring 3-dimensional position information of space points, when 6-dimensional pose information of a target to be measured is measured, three different points on the target to be measured need to be measured so as to establish a target sphere coordinate system of the laser tracker and record the target sphere coordinate system as a target sphere coordinate systemlaserTbar. The target ball of the laser tracker is fixedly arranged at the tail end of a rotating joint of the flexible mechanical arm.
By utilizing the arrangement rule of the calibration board area 202 in the camera coordinate system, a pose transformation matrix of the calibration board area in the camera coordinate system can be obtained by a PnP (Passive-n-Point) method and is recorded ascamTboardAnd then can be straightened according to the three-dimensional modelThe constant relative pose relationship between the target ball disc area 201 and the calibration plate area 202 is obtained and recorded asboardTbarFrom the above relationship, one can obtain:
laserTbar＝laserTcam camTboard boardTbar (1)
according to the measurement result of the two-dimensional code region 203 under the camera coordinate, the odd transformation matrix of the camera coordinate system relative to the laser tracker coordinate system can be further obtained as follows:
Figure GDA0002285330020000091
fixing the hand-eye camera 6 and the laser tracker 7, adjusting the task board 2 to enable the hand-eye camera 6 to effectively image the two-dimensional code area 203, and obtaining the position and posture relation of the two-dimensional code area 203 relative to the hand-eye camera 6 and the position and posture relation of the target sphere area according to the PnP algorithm, so that the actual relative position and posture relation of the center 203 of the two-dimensional code area under a camera coordinate system can be described as follows:
Figure GDA0002285330020000092
in the formula (I), the compound is shown in the specification,tagTbarand (3) a theoretical homogeneous transformation matrix between the center of the two-dimensional code area 203 and a target ball of the laser tracker is shown, and the matrix is a constant value matrix.
The measurement result of the two-dimensional code region 203 is pose information of a visual positioning two-dimensional code center in a camera coordinate system, and the two-dimensional code region 203 is fixedly arranged on the surface of the mission plate, so that the rotation centers of the two-dimensional code region 203 and the motion member are kept relatively static, and the relative relationship between the two-dimensional code region and the motion member can be obtained through calibration, which is described in detail below.
EXAMPLE six
Fig. 6 is a schematic view of interpolation solution of joint rotation centers of a synchronous measurement method for a flexible mechanical arm according to an embodiment of the present invention. ByThe target ball of the laser tracker is fixedly arranged at the tail end of the rotating joint 101, the difference of the rotating center of a single connecting rod can be solved by rotating any connecting rod k (k is I, J) in the two-degree-of-freedom joint section every time, and the direction of the rotating shaft can be determined. Rotating the I axis of the joint, and recording any 3-point T in the motion process according to the three-dimensional position data of the laser tracker 71,T2,T3Respectively is (x)1,y1,z1)、(x2,y2,z2) And (x)3,y3,z3) These three points are on one plane, namely:
Figure GDA0002285330020000101
equation (4) can be further simplified as:
A1x+B1y+C1z+D1＝0 (5)
wherein the content of the first and second substances,
Figure GDA0002285330020000102
meanwhile, the distances from the three points to the center of the space circle are equal, namely, the following equation is adopted:
Figure GDA0002285330020000103
wherein r is the radius of the space circle.
According to formula (7):
A2x+B2y+C2z+D2＝0 (8)
A3x+B3y+C3z+D3＝0 (9)
wherein the content of the first and second substances,
Figure GDA0002285330020000104
Figure GDA0002285330020000105
the following equations can be obtained for the conjunctive types (5), (8) and (9):
Figure GDA0002285330020000111
thus, T1,T2,T3The three-dimensional coordinates of the centers of the three points forming the space circle CI1 are as follows:
Figure GDA0002285330020000112
a target ball is placed at the other end of the tail end of the rotating joint 101, and any three points T in the motion process are recorded4,T5,T6Respectively are (x) in the 3-dimensional coordinates of4,y4,z4)、(x5,y5,z5) And (x)6,y6,z6) In the same way, T can be obtained4,T5,T6The three-dimensional coordinates of the centers of the three points forming the space circle CI2 are as follows:
Figure GDA0002285330020000113
wherein the content of the first and second substances,
Figure GDA0002285330020000114
Figure GDA0002285330020000115
Figure GDA0002285330020000116
linear equation xi composed of CI1 and CI2IIs the rotating shaft of the rotating joint I shaft, namely:
Figure GDA0002285330020000117
similarly, the rotation axis xi of the J axis of the revolute jointJThe equation of the straight line is:
Figure GDA0002285330020000121
wherein (x)oJ1,yoJ1,zoJ1) And (x)oJ2,yoJ2,zoJ2) Two three-dimensional coordinates of the spatial circle centers (CJ 1 and CJ2) are obtained for the axis of the rotary joint I.
Because of the space straight line xiIAnd xiJA straight line xi of the different surfaceIJThe distance of (a) is:
Figure GDA0002285330020000122
wherein the content of the first and second substances,
Figure GDA0002285330020000123
and
Figure GDA0002285330020000124
are respectively a straight line xiIAnd xiJThe direction vector of (a) is,
Figure GDA0002285330020000125
is a space point T1And T4The component spatial vector of (2).
Suppose two normalized space out-of-plane linear equations xiIAnd xiJRespectively as follows:
Figure GDA0002285330020000126
Figure GDA0002285330020000127
wherein (n)ox,I,noy,I,noz,I) And (n)ox,J,noy,J,noz,J) Are respectively a straight line xiIAnd xiJThe direction vector is unitized.
From any point p (x, y, z) in space to any one xi of two straight linesk(k ═ I, J) at a distance dkIs thus pPT1The vector formed by two points is on a straight line xikThe projection matrix of (a) is:
Figure GDA0002285330020000128
wherein the content of the first and second substances,
Figure GDA0002285330020000129
further, dkCan be expressed as:
Figure GDA00022853300200001210
wherein P and PTiRespectively representing the three-dimensional coordinates of any point in space and any point on a straight line.
The condition that any point p is the center point of the straight line of the different surface to be obtained needs to satisfy the following conditions:
Figure GDA0002285330020000131
by deriving equation (25), the coordinates of the center point of the non-coplanar straight line can be obtained as follows:
Figure GDA0002285330020000132
the intersection point p of the non-coplanar straight lines*I.e. three-dimensional coordinates of the original point O of the rotation center of the joint, and the rotation directions of the two joints are straight lines xiIAnd xiJThe direction vector of (2).
Example eight
Fig. 7 is a schematic diagram of relative poses of a joint rotation center coordinate system and a two-dimensional code center coordinate system of the synchronous measurement method for the flexible mechanical arm according to the embodiment of the present invention. Because the relative position and posture relation between the visual positioning two-dimensional code center and the laser tracker target ball at the tail end of the rotating joint 101 is fixed, the relative position and posture relation (recorded as the relative position and posture relation between the camera coordinate system and the laser tracker coordinate system) can be determined by utilizing the task boardcamTlas) By using the solving method, a homogeneous transformation matrix (recorded as a homogeneous transformation matrix) of the central coordinates of the motion member under the laser tracker can be obtainedlasTrot) The pose matrix of the visual positioning two-dimensional code center in the camera coordinate system can be directly calculated by a PnP method (recorded ascamTtag) Then, the relative pose relationship of the rotation center coordinate system with respect to the center of the two-dimensional code can be described as:
Figure GDA0002285330020000133
according to equation (27), the center of each moving member in the camera coordinate system is expressed as:
camTrot＝camTtag tagTrot (28)
thus, the spatial shape of the flexible robotic arm is made up of a collection of spatial member center points, namely:
Γshape＝{camTrot,i(1:3,4)} (29)
wherein the content of the first and second substances,camTrot,iand representing a pose matrix of the ith motion member center in a camera coordinate system.
FIG. 8 is a D-H coordinate distribution diagram of a flexible manipulator according to the synchronous measurement method of the flexible manipulator of the present invention. To be betterExpressing a kinematic model of the flexible mechanical arm, performing standard D-H coordinate system modeling on the flexible mechanical arm, and additionally adding 3 additional coordinate systems to embody the structural characteristics, and recording the additional coordinate systems as x4by4bz4b，x6by6bz6bAnd x8by8bz8bThe directions of the coordinate system are respectively equal to x4y4z4，x6y6z6And x8y8z8Are kept consistent, and the origin of the coordinate system is respectively identical with the coordinate system x3y3z3，x5y5z5And x7y7z7And the consistency is maintained.
The motion of two directions of the two-degree-of-freedom joint can directly pass through a coordinate system xiyiziAnd x(i+2)by(i+2)bz(i+2)bThe relative position and posture relationship of the two-dimensional code is described, and according to the two-dimensional code measurement result, the coordinate system homogeneous transformation matrixes with any two coincident origins are respectivelycamTrot,i、camTrot，(i+2)bThen, the homogeneous transformation matrix under the i +1 th rotation coordinate with respect to the i th rotation coordinate system is:
Figure GDA0002285330020000141
according to the 'PY-YP' freedom configuration of the flexible mechanical arm, the flexible mechanical arm is sequentially connected by two adjacent motion members (2DOF motion joints), so that the motion characteristics of the retrograded adjacent joint segments only need to be analyzed, and the motion characteristics of the whole arm are easily obtained. For an arbitrary module k, the transformation relationship from the 4 k-th coordinate system to the i-4 k +2 coordinate system is:
Figure GDA0002285330020000142
Figure GDA0002285330020000143
wherein, thetaiIs the joint angle of the 4k coordinate system.
Taking into account the respective joint angles thetai∈[-90°，90°]The simultaneous type (31) and (32) can obtain:
Figure GDA0002285330020000144
meanwhile, the joint encoder is arranged at each joint in the design of the device, the joint angle is calculated mainly according to the relative rotation quantity between the measuring magnetic ring and the induction chip, the initial state of the flexible mechanical arm and the specific arm type can be reset and calibrated through the joint encoder, and the joint encoder plays a great role in kinematic modeling and model calibration. Because the degree of freedom of the flexible mechanical arm is more various, the spatial configuration of the flexible mechanical arm is difficult to accurately obtain through kinematic modeling. According to the pose matrix of the two-dimensional code center in the camera coordinate system and the homogeneous transformation matrix of the rotation center of each motion member relative to the coordinate system of the two-dimensional code center, combining with a discrete multipoint measurement algorithm, the pose transformation matrix of any rotation center i in the camera coordinate system can be obtained as follows:
camTrot,i＝camTtagj tagjTrot,i (34)
for expressing the standard property, the pose relations of the rotation centers of all the moving members are mapped under a base coordinate system, namely:
Figure GDA0002285330020000151
further, a global vision system is used for measuring the two-dimensional code at the tail end of the flexible mechanical arm, and a pose matrix of the tail end rotation center in a camera coordinate system can be obtained by combining a pose matrix of the calibrated rotation center of the flexible mechanical arm tail end motion member relative to the two-dimensional code center on the shell and recorded as the pose matrixcamTend。
For the requirement of subsequent flexible mechanical arm motion planning, the measured terminal pose matrix needs to be mapped to a base coordinate system, and according to the two-dimensional code measurement result of the flexible mechanical arm root, the pose matrix of the flexible mechanical arm base in a camera coordinate system can be obtained as follows:
camTbase＝camTrot，0＝camTtag0 tag0Trot，0 (36)
according to the relative position relationship of the tail end of the flexible mechanical arm in the camera coordinate system and the relative position relationship of the base in the camera coordinate system, the position relationship of the tail end of the flexible mechanical arm in the base coordinate system can be calculated as follows:
Figure GDA0002285330020000152
and comparing the transformation matrix of the tail end relative to the base obtained by vision measurement and the transformation matrix of each measurement center relative to the base with the corresponding pose matrix obtained by utilizing the positive kinematics theory to obtain the shape of the flexible mechanical arm and the positioning accuracy of the tail end.
The invention realizes the synchronous measurement of the movable shape and the tail end pose of the flexible mechanical arm, and realizes the synchronous measurement function of the shape and the tail end pose of the flexible mechanical arm by combining the fusion information of the visual sensor, the joint encoder and the laser tracker.
In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

Claims (8)

1. A synchronous measurement method of a flexible mechanical arm is characterized by comprising the following steps:
acquiring typical characteristic information of the flexible mechanical arm;
converting a coordinate system to obtain the relative pose relationship among the moving base, the rotation center of each joint and the tail end of the flexible mechanical arm;
acquiring pose information of each rotary joint and the tail end of the flexible mechanical arm and relative to the hand-eye camera and the base through the relative pose relationship;
establishing a flexible mechanical arm motion model according to the pose information;
measuring pose information of a target to be measured in a camera coordinate system through a hand-eye camera, and performing hand-eye calibration by combining the pose information of the tail end of the flexible mechanical arm in a base coordinate system to obtain a pose relation of the target to be measured in the base coordinate system;
and comparing the shape and the tail end pose information of the flexible mechanical arm obtained by utilizing the typical characteristic information with the pose information obtained by measuring by the laser tracker so as to evaluate the measurement accuracy of the shape and the tail end of the flexible mechanical arm.
2. The synchronous measurement method of the flexible mechanical arm according to claim 1, wherein the typical characteristic information is obtained by shooting a two-dimensional code on each joint member and the end of the flexible mechanical arm.
3. The synchronous measurement method of the flexible mechanical arm according to claim 2, wherein the relative pose relationship is obtained according to the typical feature information and a pose transformation relationship from a two-dimensional code coordinate system to a camera coordinate system.
4. The synchronous measurement method of the flexible mechanical arm according to claim 3, wherein the relative pose relationship between the rotation center of the joint member and the two-dimensional code center is combined according to the typical characteristic information to obtain the pose relationship of each rotation center in a camera coordinate system, so as to obtain the corresponding joint angle.
5. The synchronous measurement method of the flexible mechanical arm according to claim 4, wherein the starting state of the flexible mechanical arm and the specific arm type are reset and calibrated through the joint angle so as to establish a motion model and model calibration for the flexible mechanical arm.
6. A flexible mechanical arm synchronous measurement system is characterized by comprising:
the characteristic extraction module is used for executing the steps to obtain typical characteristic information of each joint section and the tail end of the flexible mechanical arm;
the calibration conversion module is used for executing the steps and respectively acquiring the relative pose relations of the base, the rotation centers of the joints and the tail end of the flexible mechanical arm through coordinate system conversion;
the synchronous reconstruction module is used for obtaining pose information of each rotating joint and the tail end of the flexible mechanical arm relative to the base through kinematic recursion in the execution step;
the precision evaluation module is used for evaluating the shape and the tail end positioning precision of the flexible mechanical arm;
a hand-eye camera is arranged at the tail end of the flexible mechanical arm to measure pose information of the target to be measured in a camera coordinate system;
measuring pose information of a target to be measured in a camera coordinate system through a hand-eye camera, and performing hand-eye calibration by combining the pose information of the tail end of the flexible mechanical arm in a base coordinate system to obtain a pose relation of the target to be measured in the base coordinate system;
and comparing the shape and the tail end pose information of the flexible mechanical arm obtained by utilizing the typical characteristic information with the pose information obtained by measuring by the laser tracker so as to evaluate the measurement accuracy of the shape and the tail end of the flexible mechanical arm.
7. The utility model provides a flexible mechanical arm synchronous measuring device which characterized in that includes: the system comprises a flexible mechanical arm, a task board, a mobile base, a first global camera, a second global camera and a microprocessor;
the flexible mechanical arm is arranged on the movable base;
the flexible mechanical arm is provided with a plurality of rotating joints and a mechanical arm tail end device, and two-dimensional codes are arranged on the rotating joints and the mechanical arm tail end device;
the tail end of the flexible mechanical arm is provided with a hand-eye camera, and the hand-eye camera is used for measuring pose information of the target to be measured in a camera coordinate system;
the first global camera and the second global camera are arranged on one side of the mobile base and used for shooting the two-dimensional code to obtain typical feature information;
the task board is used for calibrating the parameters of the hand-eye camera;
measuring pose information of a target to be measured in a camera coordinate system through a hand-eye camera, and performing hand-eye calibration by combining the pose information of the tail end of the flexible mechanical arm in a base coordinate system to obtain a pose relation of the target to be measured in the base coordinate system;
and comparing the shape and the tail end pose information of the flexible mechanical arm obtained by utilizing the typical characteristic information with the pose information obtained by measuring by the laser tracker so as to evaluate the measurement accuracy of the shape and the tail end of the flexible mechanical arm.
8. The synchronous measuring device of the flexible mechanical arm as claimed in claim 7, wherein the task board is provided with a plurality of calibration areas, and the calibration areas comprise a target ball tray area, a calibration board area, a two-dimensional code area, a mark point area, a slit area, a circular hole area and a rectangular area.
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