Motion accuracy calibration method for surgical assistance robot

Abstract

The present application relates to a motion accuracy calibration method for a surgical assistance robot, and belongs to the field of biomedical engineering technology. The method of the present application includes: cross-arranging two groups of online projection image measuring instruments to obtain a measuring device; using the device to perform projection measurement of multiple position points in the measurement space, and based on the obtained measurement data, calculating and determining a conversion matrix used to characterize the relative position relationship between the two measuring instruments in the device; operating the surgical assistance robot to move the robot end point in the measurement space, and using the device to perform projection measurement of the trajectory points during the movement of the robot end point, and calculating and processing the obtained measurement data according to the conversion matrix to obtain the three-dimensional space coordinates of the trajectory points; based on the comparison of the measured moving distance determined by each three-dimensional space coordinate and the moving distance indicated by the robot operation instruction, the motion accuracy calibration is realized. The present application can effectively meet the accuracy requirements in the robot motion accuracy calibration process.

Description

Technical Field

[0001] The present application belongs to the field of biomedical engineering technology, and specifically relates to a motion accuracy calibration method for a surgical assistance robot. Background Art

[0002] In some surgical scenarios, such as retinal vascular injection surgery, the surgical operation space is small and the operation scale is fine. The use of relevant auxiliary robots to assist the surgery can effectively improve the doctor's operation accuracy. However, due to actual surgical needs, there are generally high requirements for the robot's motion accuracy. For example, in retinal vascular injection surgery, the diameter of the retinal blood vessels in the adult fundus is about 40~120um. It is generally believed that the motion accuracy of the fundus surgery robot must reach 10um to meet the accuracy requirements of retinal vascular injection surgery; accurately calibrating the robot's motion accuracy is conducive to optimizing the robot's motion accuracy, thereby improving the robot's absolute motion accuracy.

[0003] In the related art, commonly used methods for calibrating the robot's motion accuracy include the target ball method and the image method. The target ball method is to install a target ball on the robot's end axis and use a laser tracker to track the position of the target ball in real time to detect the trajectory of the robot's end motion for calibration. The existing general laser tracker, taking Leica AT960 as an example, has a full-range coordinate accuracy of 15um+6um / m. This accuracy cannot meet the high-precision requirements of some surgical-assisted robot calibration operations (such as the above-mentioned fundus surgery robot's motion accuracy calibration, usually the accuracy of the detection equipment in the calibration needs to be one order of magnitude higher than the robot's motion accuracy); the image method often uses an industrial camera to detect the three-dimensional position of the target point, and then calibrate the robot, but due to the limitation of pixels, the maximum detection accuracy of the existing general industrial camera is about 10um, which also cannot meet the high-precision requirements of some surgical-assisted robot calibration operations.

[0004] Therefore, for surgical assistance robots with high precision requirements, how to provide an effective and applicable motion accuracy calibration method has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] In order to overcome the problems existing in the related art at least to a certain extent, the present application provides a motion accuracy calibration method for a surgical assistance robot to solve the technical problem of how to provide an effective and applicable motion accuracy calibration method for a surgical assistance robot with high precision requirements.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] The present application provides a motion accuracy calibration method for a surgical assistance robot, the method comprising:

[0008] Arrange two groups of online projection image measuring instruments crosswise to build the measuring devices required for calibration;

[0009] Projection measurement is performed on a plurality of position points in the measurement space by the measuring device, and based on the obtained measurement data, a transformation matrix for characterizing the relative position relationship between two measuring instruments in the measuring device is calculated and determined;

[0010] The surgical assisting robot is operated to move the end point of the robot in the measurement space, the trajectory points of the robot end point during the movement are projected and measured by the measurement device, and the obtained measurement data are measured and processed according to the transformation matrix to obtain the three-dimensional space coordinates of the corresponding trajectory points;

[0011] The motion accuracy calibration is achieved by comparing the measured moving distance determined based on each of the three-dimensional space coordinates with the moving distance indicated by the robot operation instruction.

[0012] Optionally, the virtual three-dimensional measurement space coordinate systems corresponding to the two groups of online projection image measuring instruments are respectively and ; The calculation and determination of the conversion matrix and the measurement processing are performed based on the following expression:

[0013] ,

[0014] , ,

[0015] in,

[0016] P1 represents point P in the coordinate system The corresponding measurement coordinate data below, (x1z1) represents the two-dimensional projection coordinate data obtained by a measuring instrument measuring point P, Indicates that point P is The coordinates of the third dimension in the coordinate system,

[0017] P2 represents point P in the coordinate system The corresponding measurement coordinate data below, (y2z2) represents the two-dimensional projection coordinate data obtained by measuring point P by another measuring instrument, Indicates that point P is The coordinates of the third dimension in the coordinate system,

[0018] represents the transformation matrix, (c 11 c 12 c 13 c 21 c 22 c 23 c 31 c32 c 33 ) represents the elements in the transformation matrix,

[0019] (α β γ) corresponds to the rotation angle of the coordinate axis between the two virtual three-dimensional measurement space coordinate systems.

[0020] (X0Y0Z0) corresponds to the translation of the coordinate axes between the two virtual three-dimensional measurement space coordinate systems.

[0021] Optionally, the process of calculating and determining the conversion matrix includes at least one of the following operation processes:

[0022] The starting points and end points of four non-collinear and non-closed line segments in the measurement space are selected as the position points to be measured, and the unknown matrix elements in the transformation matrix are calculated and determined based on the projection measurement data corresponding to these points.

[0023] Optionally, when the operation processing process is performed more than twice, the matrix elements obtained in each operation processing process are respectively averaged, and each calculation result obtained is correspondingly determined as the matrix element in the conversion matrix.

[0024] Optionally, in the process of performing projection measurement on multiple position points in the measurement space by the measuring device, the center position of the target sphere is used as the position point to perform the projection measurement.

[0025] Optionally, the model of the online projection image measuring instrument includes KEYENCE TM-X5040.

[0026] Optionally, the detection accuracy of the online projection image measuring instrument is ±1um.

[0027] Optionally, the surgery-assisting robot includes a fundus surgery robot.

[0028] This application adopts the above technical solution, which has at least the following beneficial effects:

[0029] The motion accuracy calibration method for a surgical assistance robot in the present application includes: cross-arranging two groups of online projection image measuring instruments to build a measuring device required for calibration; performing projection measurement of multiple position points in the measurement space by the measuring device, and calculating and determining the conversion matrix used to characterize the relative position relationship of the two measuring instruments in the measuring device based on the obtained measurement data; operating the surgical assistance robot to move the robot end point in the measurement space, and performing projection measurement of the trajectory points during the movement of the robot end point by the measuring device, and calculating and processing the obtained measurement data according to the conversion matrix to obtain the three-dimensional space coordinates of the corresponding trajectory points; based on the comparison of the measured moving distance determined by each three-dimensional space coordinate and the moving distance indicated by the robot operation instruction, the motion accuracy calibration is realized. The technical solution of the present application utilizes the high accuracy of projection measurement detection, adopts two groups of online projection image measuring instruments to build a measuring device, and performs specific device correction calibration, so that the measuring device can realize high-precision measurement of the spatial position of points in the measurement space, and then uses the measuring device to realize the motion accuracy calibration of the surgical assistance robot, meeting the accuracy requirements of the motion accuracy calibration in this scenario.

[0030] Other advantages, objectives, and features of the present invention will be set forth in part in the following description, and in part will be apparent to those skilled in the art based on an examination of the following or may be taught from the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the technical solution of the present application or the prior art, and constitute a part of the specification. Among them, the accompanying drawings expressing the embodiments of the present application are used together with the embodiments of the present application to explain the technical solution of the present application, but do not constitute a limitation on the technical solution of the present application.

[0032] Figure 1 A schematic diagram of a flow chart of a motion accuracy calibration method for a surgical assistance robot provided in one embodiment of the present application;

[0033] Figure 2 This is an online schematic diagram of a linear projection image measuring instrument in one embodiment of the present application;

[0034] Figure 3 A schematic diagram illustrating a virtual three-dimensional measurement space coordinate system corresponding to two sets of online projection image measuring instruments in one embodiment of the present application;

[0035] Figure 4 It is a schematic diagram for explaining the virtual three-dimensional measurement space coordinate system corresponding to two groups of online projection image measuring instruments in one embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other implementation methods obtained by ordinary technicians in the field without creative work belong to the scope of protection of the present application.

[0037] As described in the background technology, in some surgical implementation scenarios, such as retinal vascular injection surgery, the surgical operation space is small and the operation scale is fine. The use of relevant auxiliary robots to assist the surgery can effectively improve the doctor's operation accuracy. However, due to actual surgical needs, there are generally high requirements for the robot's motion accuracy. For example, in retinal vascular injection surgery, the diameter of the retinal blood vessels in the fundus of an adult is about 40~120um. It is generally believed that the motion accuracy of the fundus surgical robot must reach 10um to meet the accuracy requirements of retinal vascular injection surgery; accurately calibrating the robot's motion accuracy is conducive to optimizing the robot's motion accuracy, thereby improving the robot's absolute motion accuracy. However, the existing target ball method and image method cannot meet the motion accuracy calibration of surgical auxiliary robots with high precision requirements.

[0038] Based on this, this application proposes a motion accuracy calibration method for a surgical assistance robot, such as Figure 1 As shown, in one embodiment, the overall implementation steps of the motion accuracy calibration method proposed in this application include:

[0039] Step S110: cross-arrange two groups of online projection image measuring instruments to build a measuring device required for calibration.

[0040] As known to those skilled in the art, an online projection image measuring instrument is an optical measuring instrument. Figure 2 The figure shows the structure of an online projection image measuring instrument. The instrument consists of a transmitter and a receiver. The measuring principle is to irradiate green LED parallel light from the transmitter. The parallel light passes through the object to be measured and forms a shadow image of the object at the receiver, thereby detecting the size information of the object. The instrument device makes use of the parallelism of light and can achieve a detection and measurement accuracy of ±1um. Based on its detection principle, the online projection image measuring instrument is used for two-dimensional scene measurement in related technologies, such as the Keyence TM-X5040 online projection image measuring instrument, which provides functions such as geometric dimension measurement, outer diameter and shape measurement, defect dimension measurement, swing and positioning measurement, etc., and can achieve a detection and measurement accuracy of ±1um.

[0041] In this application, high-precision three-dimensional measurement information is required in the motion accuracy calibration of the surgical assistance robot (for example, in one implementation scenario, the surgical assistance robot is a fundus surgery robot, and its motion accuracy is required to reach 10um, requiring at least ±1um detection and measurement accuracy). For this purpose, two sets of online projection image measuring instruments are cross-arranged to build the measurement device required for calibration, such as Figure 3 , Figure 4 As shown, Figures I and II in the figure are two cross-arranged online projection image measuring instruments.

[0042] After the measuring device is set up, step S120 is performed to perform projection measurement of multiple position points in the measuring space by the measuring device, and based on the obtained measurement data, a transformation matrix for characterizing the relative position relationship between two measuring instruments in the measuring device is calculated and determined;

[0043] It should be noted here that, for a position point p, it is obvious that a measuring instrument in the device can determine its position on a plane by projecting it, such as the position can be represented by the coordinates (x, y) in the plane rectangular coordinate system O-XY; and if the spatial position of the position point p is to be determined, a virtual coordinate axis Z orthogonal to the coordinate axis XY in the coordinate system O-XY can be constructed. * , and obtain a new spatial rectangular coordinate system (i.e., a virtual three-dimensional measurement space coordinate system). In this coordinate system, the Z coordinate of point p is determined. * Direction coordinates (i.e. Z * The coordinates of the direction are unknown); similarly, for the position point, another measuring instrument in the device can also determine the spatial coordinates of the point in similar spatial rectangular coordinates. For the two fixed measuring instruments, the position transformation relationship of the two spatial rectangular coordinate systems corresponds to the relative position relationship of the two measuring instruments. This position transformation relationship is represented by a transformation matrix in this application;

[0044] Specifically, in this embodiment, Figure 3 , Figure 4 As shown, the virtual three-dimensional measurement space coordinate system corresponding to the online projection image measuring instrument I is , the virtual three-dimensional measurement space coordinate system corresponding to the online projection image measuring instrument II is ; In this step, the conversion matrix is ​​calculated and determined based on the following expression:

[0045] (1a)

[0046] (1b)

[0047] (1c)

[0048] In the above expression, P1 represents point P in the coordinate system The corresponding measurement coordinate data below, (x1z1) represents the two-dimensional projection coordinate data obtained by measuring instrument I to point P, Indicates that point P is The coordinates of the third dimension in the coordinate system,

[0049] P2 represents point P in the coordinate system The corresponding measurement coordinate data below, (y2z2) represents the two-dimensional projection coordinate data obtained by measuring instrument II to point P, Indicates that point P is The coordinates of the third dimension in the coordinate system,

[0050] represents the transformation matrix, (c 11 c 12 c 13 c 21 c 22 c 23 c 31 c 32 c 33 ) represents the elements in the transformation matrix,

[0051] (α β γ) corresponds to the rotation angle of the coordinate axis between the two virtual three-dimensional measurement space coordinate systems.

[0052] (X0Y0Z0) corresponds to the translation of the coordinate axes between the two virtual three-dimensional measurement space coordinate systems.

[0053] Obviously, in the above expression, the transformation matrix contains 6 unknown quantities, namely the rotation angle (α β γ) and translation (X0Y0Z0) of the three axes. The coordinates of the same measurement point in the two coordinate systems contain two unknown quantities: Based on the four known quantities (x1z1y2z2), projection measurements can be performed on multiple points in the measurement space based on expressions (1a)-(1c), and calculations can be performed based on the data obtained from the projection measurements to determine the transformation matrix corresponding to the measurement device.

[0054] For example, in practice, the center position of the target ball can be used as the position point (or measurement point), and the target ball can be moved to measure at different positions to obtain the required data (equivalent to obtaining the projection measurement data of multiple position points) to calculate and determine the unknown matrix elements in the transformation matrix;

[0055] The following is a detailed description of the derivation and implementation process of this calculation:

[0056] Based on expressions (1a) to (1c), we can obtain the following system of equations:

[0057] (2)

[0058] Assume that there are two position points (for the convenience of description, they are called measurement point A and measurement point B). The coordinates of measurement point A in the two coordinate systems are recorded as: , , the coordinates of the measurement point B in the two coordinate systems are recorded as , , based on some expressions in formula (2) (the last two equations), we have:

[0059] (3)

[0060] Simplifying formula (3), we get:

[0061] (4)

[0062] eliminate :

[0063] (5)

[0064] In formula (5), It is actually a known quantity (which can be calculated based on the projected measurement data of the measuring instrument). 32 ,c 22 ,(c 21 c 32 -c 22 c 31 ),(c 23 c 32 -c 22 c 33 ), as four unknown quantities; then take 6 measurement points C to H for projection measurement. The positional relationship between these points and the two points A and B mentioned above in the measurement space needs to meet the independence requirement. Specifically, the eight measurement points A to H are connected with each other to form four line segments (AB, CD, EF, GH). These four line segments must not be collinear and closed (that is, the starting points and end points of the four line segments cannot coincide). According to the projection measurement data of the measurement points A to H, based on formula (5), it can be obtained:

[0065] (6)

[0066] The above formula is a set of four-variable linear equations, and four unknown quantities can be solved:

[0067] (7)

[0068] Substituting some results in formula (7) into formula (4), we get:

[0069] (8)

[0070] Expression (8) is for points A and B. Similarly, for the remaining points C and D, points E and F, points G and H, three pairs of equations similar to that in equation (8) can be obtained. Among the eight linear equations in total, the unknown quantity is There are 8 in total, and these unknown quantities can be determined based on these 8 equations;

[0071] After that, three non-collinear points (such as A, B, and C) are selected from point AH. According to the determined unknown quantities, nine simultaneous equations can be obtained based on equation (2), and the unknown quantities are There are 9 in total, and these unknown quantities can be determined based on these 9 equations;

[0072] At this point, all the matrix elements in the transformation matrix have been solved. It can be determined that it is easy to understand that the above process is only an example of the mathematical derivation process involved in determining the transformation matrix. Other forms of mathematical derivation calculations can also be used to determine the transformation matrix. In implementation, based on the above calculation principles, relevant software programming can be used to quickly complete the relevant calculations involved.

[0073] Regarding step S120, it should be noted that, in order to quickly complete the overall marking process, in actual operation, only the starting points and end points of four non-collinear and non-closed line segments in the measurement space can be selected as the position points to be measured (a total of 8 points), and based on the projection measurement data corresponding to these points, the above calculation method is used to calculate and determine the unknown matrix elements in the transformation matrix, that is, this operation process is performed at least once;

[0074] In order to eliminate measurement errors and improve accuracy, as a specific implementation method, the above-mentioned operation can be performed several times (i.e., 8 points are selected each time and related solutions are performed, and repeated more than twice), and then the matrix elements obtained in each operation process are averaged respectively, and the corresponding calculation results are determined as matrix elements in the transformation matrix to finally determine the transformation matrix.

[0075] Continue back Figure 1 After step S120, proceed to step S130, operate the surgical assisting robot to move the end point of the robot in the measurement space, perform projection measurement on the trajectory points during the movement of the end point of the robot by the measuring device, and calculate and process the obtained measurement data according to the transformation matrix to obtain the three-dimensional space coordinates of the corresponding trajectory points;

[0076] Specifically, the measurement process in step 130 is also based on equations (1a)-(1c). For example, in practice, the projection measurement data of the trajectory point J of the robot end point in two coordinate systems is: and , when the transformation matrix is ​​determined, the following expression can be obtained based on equations (1a)-(1c) to determine the unknown Towards coordinates,

[0077] (9)

[0078] It is easy to understand that the three-dimensional coordinates of multiple trajectory points can be determined in a similar manner.

[0079] After that, step S140 can be performed. The measured moving distance determined by the three-dimensional space coordinates obtained in step S130 is compared with the moving distance indicated by the robot operation instruction to achieve motion accuracy calibration. The specific calibration operation here is the same as the prior art, and will not be described in detail in this application.

[0080] In addition, it should be noted that, ideally, in the process of setting up the measuring device, if the two measuring instruments are arranged absolutely horizontally and orthogonally, and the origins of the two coordinate systems coincide, then it is clear that the conversion matrix does not need to be determined. Taking the above trajectory point J as an example, it can be directly used As However, this ideal situation is difficult to achieve in practice, so the above step S120 needs to be used to calibrate the measuring device.

[0081] In this application, a set of measuring devices for robot three-dimensional motion accuracy calibration is built based on a high-precision online projection image measuring instrument. This is different from the use scenario of traditional online projection image measuring instruments (the traditional use scenario is used to measure the two-dimensional shape information of objects). The use of this measuring device can realize the measurement of the three-dimensional motion trajectory of the robot with high precision, and thus can effectively meet the needs of surgical assistance robot motion accuracy calibration in reality. In this process, relevant methods are used to calibrate and correct the relative positions of the two cross-arranged measuring instruments in the measuring device, which effectively ensures the realization of measurement accuracy.

[0082] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person familiar with the technology within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A motion accuracy calibration method for a surgical assistance robot, characterized in that: include: Arrange two groups of online projection image measuring instruments crosswise to build the measuring devices required for calibration; Projection measurement is performed on a plurality of position points in the measurement space by the measuring device, and based on the obtained measurement data, a transformation matrix for characterizing the relative position relationship between two measuring instruments in the measuring device is calculated and determined; The surgical assisting robot is operated to move the end point of the robot in the measurement space, the trajectory points of the robot end point during the movement are projected and measured by the measurement device, and the obtained measurement data are measured and processed according to the transformation matrix to obtain the three-dimensional space coordinates of the corresponding trajectory points; The motion accuracy calibration is achieved based on the comparison of the measured moving distance determined by each of the three-dimensional space coordinates with the moving distance indicated by the robot operation instruction; The virtual three-dimensional measurement space coordinate systems corresponding to the two sets of online projection image measuring instruments are respectively and ; The calculation and determination of the conversion matrix and the execution of the measurement process are performed based on the following expression: （1a）， （1b）， （1c）， in, Indicate point In the coordinate system The corresponding measurement coordinate data is as follows: Indicates that a measuring instrument is used to measure a point The two-dimensional projection coordinate data obtained by measurement, Indicates that point P is The coordinates of the third dimension in the coordinate system, Indicate point In the coordinate system The corresponding measurement coordinate data is as follows: Indicates that another measuring instrument is used to measure the point The two-dimensional projection coordinate data obtained by measurement, Indicates that point P is The coordinates of the third dimension in the coordinate system, represents the transformation matrix, represents the elements in the transformation matrix, Correspondingly represents the rotation angle of the coordinate axis between the two virtual three-dimensional measurement space coordinate systems, The corresponding coordinate axis translation between the two virtual three-dimensional measurement space coordinate systems; When the projection measurement data of the trajectory point of the robot end point in the two coordinate systems is, and ,but The coordinates are determined by the following expression: The three-dimensional coordinates of multiple trajectory points are determined in the same way; The process of determining the conversion matrix includes at least one of the following operations: The starting points and end points of four non-collinear and non-closed line segments in the measurement space are selected as the position points to be measured, and the unknown matrix elements in the transformation matrix are calculated based on the projection measurement data corresponding to these points; wherein, based on expressions 1a to 1c, the equation group can be obtained: （2） Assume that there are two position points, measurement point A and measurement point B. The coordinates of measurement point A in the two coordinate systems are recorded as: , , the coordinates of the measurement point B in the two coordinate systems are recorded as , , based on the last two equations in expression 2, we have: （3） Simplifying Expression 3, we get: （4） erase : （5） In expression 5, It is actually a known quantity and can be calculated based on the projected measurement data of the measuring instrument. As four unknown quantities; then take 6 measurement points C to H for projection measurement. The positional relationship between these points and points A and B in the measurement space needs to meet the independence requirement. Specifically, the 8 measurement points A to H are connected with each other, which can form four line segments AB, CD, EF, GH. These four line segments must not be collinear and closed, that is, the starting points and end points of the four line segments cannot coincide. According to the projection measurement data of measurement points A to H, based on expression 5, we get: （6） The above formula is a system of four-variable linear equations, so four unknown quantities can be solved: (7) Substituting part of the result in Expression 7 into Expression 4, we get: （8） Expression 8 is for points A and B. Similarly, for the remaining points C and D, points E and F, points G and H, three pairs of equations similar to that in Expression 8 can be obtained. Among the 8 linear equations in total, the unknown quantity is There are 8 in total, and these unknown quantities can be determined based on these 8 equations; After that, we select three non-collinear points from point AH. According to the determined unknown quantities, we can get 9 simultaneous equations based on expression 2, and the unknown quantity is There are 9 in total, and these unknown quantities can be determined based on these 9 equations; When the operation process is performed more than twice, the matrix elements obtained in each operation process are respectively averaged, and the obtained calculation results are correspondingly determined as the matrix elements in the conversion matrix.

2. The motion accuracy calibration method according to claim 1, characterized in that: In the process of performing projection measurement on multiple position points in the measurement space by the measurement device, the center position of the target ball is used as the position point to perform the projection measurement.

3. The motion accuracy calibration method according to claim 1, characterized in that: The detection accuracy of the online projection image measuring instrument is ±1um.

4. The motion accuracy calibration method according to claim 3, characterized in that: Models of the online projection image measuring instrument include KEYENCE TM-X5040.

5. The motion accuracy calibration method according to any one of claims 1 to 4, characterized in that: The surgical assistance robot includes a fundus surgery robot.

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