CN-116942314-B - Positioning method and system for mixing optical positioning and mechanical positioning

CN116942314BCN 116942314 BCN116942314 BCN 116942314BCN-116942314-B

Abstract

The invention discloses a positioning method and a system for mixing optical positioning and mechanical positioning, which belong to the technical field of surgical navigation, wherein the method comprises the steps of carrying out high-precision calibration and calibration on the system by adopting an optical calibration mode before surgery; in operation, pose measurement is carried out on a target object by adopting a non-shielding mechanical positioning mode, wherein the non-shielding mechanical positioning mode comprises the steps of obtaining a transfer matrix of the object relative to a reference system according to the angle number read by an encoder at each joint in real time and a kinematic model obtained by an optical calibration mode before operation, so as to calculate and obtain the relative position and the pose of the measured object. Through the processing scheme disclosed by the invention, the flexibility of optical calibration and the accuracy of mechanical positioning are combined, so that the cost can be reduced and the high absolute positioning accuracy of the operation in a narrow space can be ensured.

Inventors

LIU FANGDE
GUO QINGXUAN
YANG LIANGZHU
LANG JUNWEI
Lv Cunce
LI LIANJIE
LIU YUE

Assignees

杭州湖西云百生科技有限公司

Dates

Publication Date: 20260508
Application Date: 20230719

Claims (1)

1. A hybrid optical and mechanical positioning system comprising: The mechanical arm is provided with a plurality of joints, and each joint is provided with an encoder; the optical identification points are used in the preoperative calibration process, are fixed on all connecting rods of the mechanical arm, and the pose changes along with the movement of the mechanical arm and are used for real-time online calibration; the optical tracker is used in the preoperative calibration process, is fixed in the space outside the mechanical arm body, is unchanged from the pose of the world coordinate system, and is used for reading the relative positions of the optical identification points on the connecting rods in real time, so that the following method is realized: Before operation, performing high-precision calibration and calibration on the system by adopting an optical calibration mode, wherein the optical calibration mode comprises the steps of collecting and recording dot matrix data by rotating each joint of the mechanical arm, performing fitting treatment on a combined track, and calculating to obtain DH parameters, and finally obtaining an accurate kinematic model of the mechanical arm; in operation, carrying out pose measurement on a target object by adopting a non-shielding mechanical positioning mode, wherein the non-shielding mechanical positioning mode comprises the steps of obtaining a transfer matrix of the object relative to a reference system according to the angle number read by an encoder at each joint in real time and a kinematic model obtained by an optical calibration mode before operation, so as to calculate and obtain the relative position and pose of the measured object; Before operation, the system is calibrated by adopting an optical calibration mode, and the method comprises the following steps: arranging an optical identification lattice for space positioning on each joint connecting rod of the mechanical arm; When calibration data are acquired, the lattice coordinates of the optical identification points are captured by an optical tracker through rotating each joint connecting rod of the mechanical arm, so that a formed combined track is obtained; The acquired 3D track A of the joint 1 is converted into a 2D track A c through singular value decomposition fitting to obtain a rotation plane, thereby obtaining a normal vector of the rotation plane I.e. coordinate system The shaft, the calculation process is as follows: Wherein, the A set of three-dimensional points is represented, The normalized and centered measurement points are represented, U represents the eigenvalues, S represents the matrix with the eigenvalues as the principal diagonal in the singular value decomposition, Representing the matrix spanned by the eigenvectors, B representing the right-hand orthogonal basis, A determinant of a matrix representing a principal diagonal of eigenvalues in the singular value decomposition, Representing the columns of the right hand orthogonal base, Representing the projection of the measurement point in two-dimensional euclidean space, The projection matrix is represented by a matrix of projections, Representing a centered measurement point; The 2D track fitting of the joint 1 is converted into a 2D circle, so that the radius r 1 of the circle and the circle center o 1 are obtained, the circle center o 1 is used as the origin of the coordinate system of the joint 1, and the calculation process is as follows: Wherein, the A matrix representing a system of linear equations consisting of a projection of the measurement point in a two-dimensional euclidean space and a unit of one, Representing the unknown parameters of the system of linear equations, Representing coordinates of a two-dimensional circle, c1, c2, k3 representing unknown parameters to be solved, Representing a three-dimensional point set; after the motion trail fitting of each joint is completed, the rotation axis of each joint is obtained And the origin of the coordinate system ; Through the rotation axis of each joint And the origin of the coordinate system Setting a corresponding DH coordinate system according to the coordinate system establishment rule; calculating DH parameters, and obtaining an accurate kinematic model of the mechanical arm according to the kinematic model formula (1) and the kinematic model formula (2); Formula (1): formula (2): Wherein M represents a transfer matrix, θ represents a rotation angle around a z axis, a represents a link length, α represents a joint torsion angle, and d represents a joint offset; In the operation, the pose measurement is carried out on the target object by adopting a non-shielding mechanical positioning mode, and the method comprises the following steps: The angle number theta i of each joint is read in real time through the encoder at each joint, and communication control is carried out with the upper computer through a high-performance bus; According to the obtained angle degree theta i , combining a kinematic model formula (1) and a formula (2) obtained by means of preoperative optical calibration, and obtaining a transfer matrix M of the object relative to a reference system; the relative position and posture of the measured object are obtained by calculation according to the formula (3), Equation (3): Wherein, the Representing the pose of the measured object, M representing the transfer matrix, Representing the pose of the measured object in the tool-end reference system.

Description

Positioning method and system for mixing optical positioning and mechanical positioning Technical Field The disclosure relates to the technical field of surgical navigation, in particular to a positioning method and a system for mixing optical positioning and mechanical positioning. Background With the continuous development of science and technology, surgical robots are becoming more and more popular. To ensure intra-operative safety, surgical robots are required to have high absolute positioning accuracy. At present, the clinically common positioning modes include optical positioning and mechanical positioning, wherein the optical positioning is used for judging the relative position of an object in space through optical capturing, and the mechanical positioning is used for determining the relative position of the object through pure kinematics. The two modes have certain problems that 1) the optical positioning mode ① is greatly interfered by external environment factors, when other reflection points or optical identification points are blocked in a test environment, the calibration precision and the reliability of a calibration result are reduced, the ② space measurement range is large, the target is large, and the method is not suitable for operation positioning in a narrow space, and 2) the mechanical positioning mode is small in mechanical parts, small in space measurement range and free from blocking, but has mechanical abrasion phenomenon, so that the precision is reduced, and the calibration maintenance is required to be periodically repeated. In order to solve the problems, the invention discloses a positioning method of mixing optical positioning and mechanical positioning, which combines the flexibility of optical calibration and the accuracy of mechanical positioning by mixing two positioning modes, so that the system has high absolute positioning accuracy, simultaneously reduces the cost, improves the adaptability of a surgical navigation system, and enables the surgical (such as oral surgery) positioning in a narrow space to be possible. Disclosure of Invention In view of the above, embodiments of the present disclosure provide a positioning method and a system for mixing optical positioning and mechanical positioning, so as to at least partially solve the problems in the prior art. In a first aspect, embodiments of the present disclosure provide a positioning method of optical positioning and mechanical positioning hybrid, including: Before operation, performing high-precision calibration and calibration on the system by adopting an optical calibration mode, wherein the optical calibration mode comprises the steps of collecting and recording dot matrix data by rotating each joint of the mechanical arm, performing fitting treatment on a combined track, and calculating to obtain DH parameters, and finally obtaining an accurate kinematic model of the mechanical arm; In operation, pose measurement is carried out on a target object by adopting a non-shielding mechanical positioning mode, wherein the non-shielding mechanical positioning mode comprises the steps of obtaining a transfer matrix of the object relative to a reference system according to the angle number read by an encoder at each joint in real time and a kinematic model obtained by an optical calibration mode before operation, so as to calculate and obtain the relative position and the pose of the measured object. According to a specific implementation manner of the embodiment of the present disclosure, the performing high-precision calibration on the system by adopting an optical calibration manner before operation includes: arranging an optical identification lattice for space positioning on each joint connecting rod of the mechanical arm; When calibration data are acquired, the lattice coordinates of the optical identification points are captured by an optical tracker through rotating each joint connecting rod of the mechanical arm, and a formed combined track is obtained. According to a specific implementation manner of the embodiment of the present disclosure, the high-precision calibration is performed on the system by adopting an optical calibration manner before operation, and the method further includes: The acquired 3D track A of the joint 1 is converted into a 2D track A c through singular value decomposition fitting to obtain a rotation plane, thereby obtaining a normal vector of the rotation plane Namely the z 1 axis of the coordinate system, the calculation process is as follows: A=[x1 x2…xN] wherein, [ x 1 x2…xN ] represents a three-dimensional point set, The normalized and centered measurement points are represented by U, S, the matrix with the eigenvalue of the singular value decomposition as the principal diagonal, V T, the matrix with the eigenvector of the matrix, B, the right-hand orthogonal base, det (U), the determinant of the matrix with the eigenvalue of the principal diagonal in the singular value decompositi