Online compensation method for reset pose error of long bone fracture surgical robot

Abstract

The invention discloses an online compensation method for reset pose errors of a long bone fracture surgical robot. The online compensation method comprises the steps that a target pose matrix # imgabs0 # is obtained through preoperative path planning, # imgabs1 # and # imgabs2 # are obtained through robot calibration, and the joint position theta temp is obtained through a robot inverse kinematics numerical method; s3, inputting the theta temp obtained in the step S3 into a robot controller, and enabling the robot to move to a theoretical target pose; measuring a current pose # imgabs3 # after the movement of S4 through an optical positioning system; calculating an error differential operator delta T between the obtained current pose # imgabs4 # and the target pose matrix # imgabs5 #; calculating an error motion vector delta d according to the obtained delta T; adopting the delta d to judge whether the delta d2 is smaller than a threshold value epsilon or not; if yes, compensation is stopped; if not, entering the next step; and according to the initial target pose # imgabs6 # and the error motion vector delta d, calculating a stage target pose # imgabs7 #, and according to the stage target pose # imgabs8 #, obtaining new # imgabs9 # and # imgabs10 #, and repeatedly iterating the S2-S8.

Description

Technical Field

[0001] The present invention relates to the technical field of robot manufacturing and debugging, and in particular to an online compensation method for resetting posture errors of a long bone fracture surgery robot. Background Art

[0002] During the manufacturing, installation and debugging of the robot, certain errors will be introduced. In addition, problems such as clearance and wear that may occur in the transmission system during long-term operation will further accumulate errors. These factors work together and may lead to parameter errors in the robot's connecting rods, so that when the robot performs a motion task, there is a deviation between the actual position reached and the predetermined theoretical position. Therefore, taking appropriate compensation measures is the key to ensuring its precise positioning and efficient execution.

[0003] The robot end-effector posture error compensation method is an effective strategy to improve posture accuracy. It mainly includes two categories: offline compensation and online compensation. The offline compensation strategy measures the error of a series of end-effector postures in the robot's workspace and builds the robot's motion error model based on these data. In this way, the possible posture deviation can be accurately estimated and corrected before the robot is operated, thereby significantly improving the positioning accuracy of the robot when performing tasks. Robot kinematic parameter calibration is a commonly used offline compensation method. Existing literature has proposed a kinematic model parameter calibration method considering the robot base coordinate system posture error, a kinematic parameter error calibration method based on the robot end distance error, a posture error compensation method based on a spatial grid, an industrial robot positioning error compensation method based on a CNC system drive, and an equivalent posture error of the robot end effector to the input error of the driving joint. The robot error model is established with the joint input as the independent variable, and the effectiveness of the model is verified through offline identification and online compensation experiments. However, the offline compensation method cannot compensate for the posture error caused by the environment, load, etc. when the robot is working, and the degree of improvement in posture accuracy is limited.

[0004] The online compensation method for the robot end posture error uses high-precision measurement equipment to obtain the robot end posture error, and then corrects the robot end posture through the error compensation algorithm, so that the robot can continuously adjust the end posture to approach the target posture during the working process, which is real-time. The existing online compensation method is to calculate the error between the actual posture of the robot and the target posture based on the data fed back by the laser tracker, and then compensate the posture error online through the robot sensor interface provided by the KUKA robot, but this method does not give the specific calculation process of converting the posture error to the joint error. There is also an online adaptive compensation method for the positioning error of an industrial robot, which ensures that the online compensation accuracy meets the requirements by autonomously judging the change of the error level and adaptively optimizing the posture mapping model method, but this method is cumbersome and complicated. The laser tracker is used to measure the robot end position in real time, and the external disturbance is identified through the second-order disturbance observer. On the basis of the disturbance observation, the sliding mode controller is used to complete the robust control of the robot, thereby improving the absolute positioning accuracy of the robot, but no error compensation is performed on the robot end posture. The above online compensation methods all use expensive laser trackers to feedback the robot posture error.

[0005] Surgical tools are installed at the end of the surgical robot, and certain errors will occur during the installation process. The influence of the surgical robot's geometric error, non-geometric error and system error will cause a deviation between the expected position and actual position of the robot end during the operation.

[0006] On the other hand, the surgical system includes the robot base coordinate system, the patient space coordinate system, and the image space coordinate system. The registration accuracy between these coordinate systems has a great influence on the position accuracy of the surgical robot end. The positioning accuracy of the surgical tools installed at the end of the robot in the patient space determines the accuracy of the surgical system in performing surgical fracture reduction.

[0007] It is not difficult to see that there are still many problems in the existing technology, and it is necessary to improve the existing compensation method for the resetting posture error of the surgical robot to overcome the defects of the existing technology. Summary of the invention

[0008] Therefore, in order to solve the above problems in the prior art, the present invention proposes an online compensation method for resetting posture errors of a long bone fracture surgical robot.

[0009] The present invention solves the above problems by the following technical means:

[0010] An online compensation method for resetting posture error of a long bone fracture surgical robot, comprising:

[0011] S1. Obtain the target pose matrix through preoperative path planning

[0012] S2. Obtain the transformation relationship between the coordinate system of the optical positioning system in the surgical robot system and the robot base coordinate system through robot calibration And the transformation relationship between the coordinate system of the optical tool and the coordinate system of the end of the robot arm

[0013] S3, obtained from S2 and Using the robot inverse kinematics numerical method to obtain the joint position θ temp ;

[0014] S4, the θ obtained in S3 temp Input the robot controller to make the robot move to the theoretical target position;

[0015] S5, measuring the current position and posture after the movement in S4 through the optical positioning system

[0016] S6, the current posture obtained by calculating the S5 With the target pose matrix The error differential operator ΔT between them;

[0017] S7, calculating an error motion vector Δd according to the ΔT obtained in S6;

[0018] S8, using the Δd obtained in S7, determining whether the ||Δd||2 is less than a threshold value ε; if so, the compensation stops; if not, proceeding to S9;

[0019] S9, based on the initial target posture in S1 and the error motion vector Δd obtained in S7 to calculate the phased target posture According to the stage target posture Derive new and The steps S2-S8 are iterated repeatedly.

[0020] Furthermore, the surgical robot system in S2 includes:

[0021] A robotic arm is used to perform surgery; an optical positioning system is used to determine the position of the robotic arm and bones during surgery.

[0022] Furthermore, the optical positioning system includes: an optical locator, an optical tool T1, an optical tool T2 and an optical tool T3, wherein the optical tool T1, the optical tool T2 and the optical tool T3 are all provided with an infrared reflection ball, and the optical locator is located on one side of the robotic arm, and the optical locator obtains the position of the center point of the passive optical tool in the optical positioning system coordinate system by tracking the infrared reflection ball;

[0023] The optical tool T1 is disposed at the proximal bone position and is used to determine the position and posture of the proximal bone;

[0024] The optical tool T2 is arranged at the distal bone position and is used to determine the position and posture of the distal bone;

[0025] The optical tool T3 is arranged on the flange at the end of the robot arm and is used to measure and calculate the end position of the robot.

[0026] Furthermore, the θ temp The calculation method is:

[0027] pass Calculate the relationship between the flange and the base coordinate system. Perform inverse kinematics calculation to obtain θ temp .

[0028] Furthermore, the calculation formula of the differential operator ΔT is:

[0029] R represents the rotation matrix; t represents the translation matrix.

[0030] Further, in said S7:

[0031] Δd=[dx,dy,dz,δx,δy,δz] T .

[0032] Furthermore, the threshold ε in S8 is 2 mm.

[0033] The present invention calculates the robot reset target posture and the robot arm joint angle in the optical positioning system based on the result of the path planning of fracture reduction, moves the robot arm to obtain the robot reset actual posture, and iteratively changes the robot joint angle through the compensation method, so that the robot reset actual posture gradually approaches the target posture. In the subsequent iteration process, the posture error fluctuates greatly and is difficult to converge to a stable value. In contrast, the online compensation of the reset posture error does not increase the position error, and the posture error fluctuates less during the iteration process, which can make the robot reset posture gradually approach the target posture. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1It is a flow chart of the online compensation method for the resetting posture error of the surgical robot according to the present invention;

[0036] Figure 2 It is a schematic diagram of the structure of the surgical robot system described in the present invention. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be pointed out that the described implementation examples are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1

[0039] The present invention is described in more detail below:

[0040] It should be noted that the various values ​​calibrated by the robot described in the present invention are all determined by optical locators and optical tools to determine the end position of the robot, and then the relationship between the end and the robot base coordinate system is inversely solved based on the end position of the robot, and finally the relationship between the optical locator and the robot base coordinate system is solved.

[0041] like Figure 1 As shown, an online compensation method for the resetting posture error of a long bone fracture surgical robot comprises:

[0042] S1. Obtain the target pose matrix through preoperative path planning It should be noted that the The value of can be known during path planning before surgery, where P represents the proximal bone and D represents the distal bone.

[0043] S2. Obtain the transformation relationship between the coordinate system of the optical positioning system in the surgical robot system and the robot base coordinate system through robot calibration (C represents the optical locator, B represents the robot base coordinate system), and the transformation relationship between the coordinate system of the optical tool and the coordinate system of the end of the robot arm (F represents the robot end flange, and the lower left subscript T represents the optical tool); It should be noted that the transformation relationship between the coordinate system of the optical positioning system and the robot base coordinate system is The transformation relationship between the coordinate system of the optical tool and the coordinate system of the end of the robot arm The value of can be obtained through robot calibration.

[0044] like Figure 2As shown, preferably, the surgical robot system in S2 includes:

[0045] A mechanical arm is used to perform surgery; an optical positioning system is used to determine the position of the mechanical arm and bones during surgery. Preferably, the optical positioning system includes: an optical positioning instrument, an optical tool T1 (i.e. Figure 2 Optical tool 1), optical tool T2 (i.e. Figure 2 Optical tool 2) and optical tool T3 (i.e. Figure 2 The optical tool T1, the optical tool T2 and the optical tool T3 are all equipped with an infrared reflection ball. The optical locator is located on one side of the robotic arm. The optical locator obtains the position of the center point of the passive optical tool in the coordinate system of the optical positioning system by tracking the infrared reflection ball. The optical tool T1 is set at the proximal bone position to determine the posture of the proximal bone. The optical tool T2 is set at the distal bone position to determine the posture of the distal bone. The optical tool T3 is set on the flange at the end of the robotic arm. The optical locator can measure and calculate the posture of the robot end.

[0046] It should be noted that the optical tool T3 in the figure is used as an important positioning tool for connecting the robot end tool and for online end compensation. The optical tool T1 is used to determine the posture of the proximal bone and the optical tool T2 is used to determine the posture of the distal bone. The posture relationship of the proximal bone relative to the optical locator is: (Where: That is, the homogeneous expression of the optical tool T1 under the optical positioning system; It can be obtained by robot calibration, indicating the relative relationship of the proximal bone to the optical tool T1); Similarly, the position and posture of the flange origin and the robot base coordinate system can be expressed as ( Indicates the target position relationship of the distal bone relative to the proximal bone; represents the relative relationship between the optical tool T2 and the distal bone, Directly acquired by the optical positioning system; Determined by the assembly relationship between the optical tool T3 and the end flange, the transformation matrix between the optical positioning system coordinate system and the robot base coordinate system is calibrated by the robot).

[0047] S3, obtained from S2 and Using the robot inverse kinematics numerical method to obtain the joint position θ temp Preferably, the joint position θ temp The calculation method is:

[0048] pass Calculate the relationship between the end flange and the robot base coordinate system. Perform inverse kinematics calculation to obtain θ temp .

[0049] S4, the θ obtained in S3 temp Input the robot controller to make the robot move to the theoretical target position;

[0050] S5, measuring the current position and posture after the movement in S4 through the optical positioning system The current pose This can be derived from the optical tool pose on the proximal and distal bones.

[0051] S6, the current posture obtained by calculating the S5 With the target pose matrix The error differential operator ΔT between them; preferably, the calculation formula of the differential operator ΔT is:

[0052] R represents the rotation matrix; t represents the translation matrix.

[0053] S7, calculating the error motion vector Δd according to the ΔT obtained in S6; it should be noted that the expression of the motion vector Δd is:

[0054] Δd=[dx,dy,dz,δx,δy,δz] T , where dx, dy, dz represent the error in the xyz direction, that is, the translation vector, and δx, δv, δz represent the error around the xyz Euler angle, that is, the rotation vector.

[0055] S8. Use the Δd obtained in S7 to determine whether the ||Δd2 is less than a threshold value ε; if so, stop compensation; if not, proceed to S9; preferably, the threshold value ε is 2 mm.

[0056] S9, based on the initial target posture in S1 and the error motion vector Δd obtained in S7 to calculate the phased target posture According to the stage target posture Derive new and Repeat the iterations of S2-S8. Preferably, the phased target posture The calculation formula is:

[0057] The target position of the distal bone relative to the proximal bone is obtained by the preoperative path planning of the reduction. The current position of the proximal bone and the distal bone is calculated based on the target position and the optical tools T1, T2 and T3, so as to finally calculate ΔT.

[0058] Since the angle change is very small and can be ignored, the Δd here is approximately equal to the distance error. Use ||Δd||2 to determine whether it is less than the threshold. If it is greater than the threshold, subtract Δd from the target posture to obtain the stage target posture, and calculate the joint angle through the robot inverse kinematics. The joint angle is input into the robot controller to drive the robot to move. The distal bone posture at this time is the second current distal bone posture. Then, the above-mentioned differential operator calculation method is used to perform online compensation for the robot reset error. The maximum number of iterations is set to obtain the error compensation result. All errors of the result are based on the initial target posture.

[0059] The present invention calculates the robot reset target posture and the robot arm joint angle in the optical positioning system based on the result of the path planning of fracture reduction, moves the robot arm to obtain the robot reset actual posture, and iteratively changes the robot joint angle through the compensation method, so that the robot reset actual posture gradually approaches the target posture. In the subsequent iteration process, the posture error fluctuates greatly and is difficult to converge to a stable value. In contrast, the online compensation of the reset posture error does not increase the position error, and the posture error fluctuates less during the iteration process, which can make the robot reset posture gradually approach the target posture.

[0060] References to "one embodiment", "another embodiment", "embodiment", "preferred embodiment", etc. in this specification refer to specific features, structures or characteristics described in conjunction with the example included in at least one embodiment generally described in this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Further, when a specific feature, structure or characteristic is described in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the present invention. Although the present invention is described herein with reference to a number of illustrative examples of the present invention, it should be understood that those skilled in the art can design many other modifications and implementations that fall within the scope and spirit of the principles disclosed in this application. More specifically, within the scope of the present application disclosure, drawings and claims, in addition to the deformation and improvement that can be made to the components and / or layout of the subject combination layout, other uses will also be obvious to those skilled in the art.

Claims

1. An online compensation method for the resetting posture error of a long bone fracture surgical robot, characterized in that: include: S1. Obtain the target pose matrix through preoperative path planning S2. Obtain the transformation relationship between the coordinate system of the optical positioning system in the surgical robot system and the robot base coordinate system through robot calibration And the transformation relationship between the coordinate system of the optical tool and the coordinate system of the end of the robot arm S3, obtained from S2 and Using the robot inverse kinematics numerical method to obtain the joint position θ temp ; S4, the θ obtained in S3 temp Input the robot controller to make the robot move to the theoretical target position; S5, measuring the current position and posture after the movement in S4 through the optical positioning system S6, the current posture obtained by calculating the S5 With the target pose matrix The error differential operator ΔT between them; S7, calculating an error motion vector Δd according to the ΔT obtained in S6; S8, using the Δd obtained in S7, determining whether the ||Δd||2 is less than a threshold value ε; if so, the compensation stops; if not, proceeding to S9; S9, based on the initial target posture in S1 and the error motion vector Δd obtained in S7 to calculate the phased target posture According to the stage target posture Derive new and The steps S2-S8 are iterated repeatedly.

2. The online compensation method for the resetting posture error of the long bone fracture surgical robot according to claim 1 is characterized in that: The surgical robot system in S2 comprises: A robotic arm is used to perform surgery; an optical positioning system is used to determine the position of the robotic arm and bones during surgery.

3. The online compensation method for the resetting posture error of the long bone fracture surgical robot according to claim 2 is characterized in that: The optical positioning system includes: an optical locator, an optical tool T1, an optical tool T2 and an optical tool T3, wherein the optical tool T1, the optical tool T2 and the optical tool T3 are all provided with an infrared reflection ball, and the optical locator is located on one side of the robotic arm, and the optical locator obtains the position of the center point of the passive optical tool in the optical positioning system coordinate system by tracking the infrared reflection ball; The optical tool T1 is disposed at the proximal bone position and is used to determine the position and posture of the proximal bone; The optical tool T2 is arranged at the distal bone position and is used to determine the position and posture of the distal bone; The optical tool T3 is arranged on the flange at the end of the robot arm and is used to measure and calculate the end position of the robot.

4. The online compensation method for the resetting posture error of the long bone fracture surgical robot according to claim 2 is characterized in that: The θ temp The calculation method is: pass Calculate the relationship between the flange and the base coordinate system. Perform inverse kinematics calculation to obtain θ temp .

5. The online compensation method for the resetting posture error of the long bone fracture surgical robot according to claim 1 is characterized in that: The calculation formula of the differential operator ΔT is: R represents the rotation matrix; t represents the translation matrix.

6. The online compensation method for the resetting posture error of the long bone fracture surgical robot according to claim 1 is characterized in that: In the S7: Δd=[dx,dy,dz,δx,δy,δz] T 。 7. The online compensation method for the resetting posture error of a long bone fracture surgical robot according to claim 1 is characterized in that: The threshold ε in S8 is 2 mm.

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