Six degrees of freedom positioning compensation method of robotic arm-assisted medical bone drilling

Abstract

The positioning accuracy of medical bone drilling has a great impact on the success rate of orthopedic surgery. Due to the need for high accuracy of medical bone drilling, with use of any 6-DoF-type robotic arm to assist in drilling, a novel six-degree-of-freedom compensation positioning algorithm of robotic arm-assisted medical bone drilling is proposed, in which only position but also orientation errors of robotic end are considered, increasing positioning capability of drilling instrument end effector with position and orientation correction for medical drilling motion accurate controlling. For the different position and orientation characteristics of the robot arm controlling and measurement point/zone, position and orientation transformation from measurement to controlling point/zone is established through position and angle calibration experiments, realizing position and orientation error measured by optical tracking system from measurement point/zone to controlling point/zone. Based on 6-DoF parameter and principle of robotic arm, a positioning compensation model based on the 6-DoF position and orientation errors of robotic arm end is proposed, and iteration cycle is used for higher accuracy, realizing double correction of position and orientation of robotic arm end. The accuracy verification experiments measured by the optical tracking system shows that the average position error before and after the 6-DoF compensation positioning algorithm reduces from 1.42 mm (before compensation with DH-based inverse kinematic model) to 0.20 mm (after compensation model) and the average angle error from 0.470° to 0.046°. A bovine spine drilling experiment is carried out based on the 6-DoF compensation algorithm, and the average position error of the hole in the specific direction measured by the contour projector is 0.221 mm, achieving high positioning accuracy of bone drilling, demonstrating reliability and practical application value of medical bone drilling with the compensation of positioning algorithm.