Flexible Needle Control Based On Needle Tip Pose Recognition And Force Feedback

When the bevel tip flexible needle performs a puncture motion in soft tissue,the soft tissue exerts a force on the inclined surface of the needle tip,which deflects the puncture path of the flexible needle.By controlling the feed and rotation of the needle,the needle tip pose can be adjusted to achieve the desired puncture path and finally hit the target.In this paper,with the help of ultrasonic imaging equipment and force sensor,combined with the deflection characteristics of flexible needle puncturing soft tissue,research on flexible needle control based on needle tip pose and force feedback is proposed.First,based on the ultrasound image,the position of the needle tip was extracted and the three motion modes of the probe tracking the needle tip were analyzed.The ultrasound image of the needle cross-section is obtained by scanning the needle radially and vertically with the ultraso nic probe,and the comet-tail-like needle cross-sectional image in the ultrasound image is processed by median filtering,binarization,expansion and corrosion.Then the pixel coordinates of the needle cross-sectional center can be extracted by Huff linear transformation.According to the parameter setting of the ultrasound imaging device,the corresponding relationship between the pixel and actual size in the ultrasound image can be analyzed,so as to realize the transformation between the pixel coordinates of the needle cross-sectional center and the actual coordinates.After separately analyzing the three motion models of the ultrasonic probe tracking the needle tip,this paper uses a robust reciprocating motion of the ultrasonic probe to track the needle tip.Secondly,based on the force feedback data,a needle tip torsion lag model for puncturing soft tissue was established,and the online detection of the needle bending curvature was realized based on the coordinate data of the needle cross-sectional center.The friction between the flexible needle and the tissue will cause the torsional lag of the needle tip,that is,the rotation angle of the needle tip always lags behind the needle tail.The relationship between the lag angle and force is then analyzed experimentally.According to the puncture experiments,the indirect feed-forward Kalman filter is used to process the coordinate data of the needle cross-sectional center extracted by the ultrasonic probe for reciprocating tracking of the needle tip,so as to achieve more accurate online detection of needle bending curvature.Thirdly,based on the improved RRT algorithm for path planning,according to the path evaluation function and the characteristics of flexible needle deflection,the path is dynamically planned and the path points are generated to achieve movement control based on needle tracking and needle deflection.By analyzing the deflection characteristics of the flexible needle,the RRT algorithm was improved,the path planning speed was improved,and the optimal path was selected according to the path evaluation function to generate path points.Finally,the puncture control of the flexible needle was achieved based on the ultrasound image and force feedback.Finally,the relationship between the lag angle and force was analyzed through the needle tip torsion lag experiment,and a target puncture experiment was performed in the presence of obstacles.The experimental results were analyzed to verify the accuracy of the flexible needle control based on needle tip pose recognition and force feedback.This paper is mainly based on needle tracking using the ultrasound image and a needle tip torsion lag model established by force feedback to achieve deflec tion control of flexible needle.A needle tip tracking method based on the two-dimensional ultrasound image is proposed.The needle tip torsion lag angle is compensated based on force feedback.The improved RRT algorithm is used for dynamic path planning to generate path points,and experimental verification is performed to provide theoretical and experimental basis for flexible needle puncture control based on needle tip pose recognition and force feedback.