| The robot assisted surgery has been greatly supported and promoted by doctors, medical institutions, robotics researchers and industry, and it becomes a hot field of bio-medical engineering and Robot R&D, due to its obvious advantages in improving medical care efficiency and patient well-being, since it was firstly applied in 1985. But with the introduction of complex systems, more challenges are presented for doctors’ skills and medical robot system. It shows that the robot is currently introduced into the medical field as an intelligent tool for doctors, therefore human-robot interaction issue has become an obstacle to limit medical robot to entering the medical field.Based on this, this research designs a lightweight interactive robot in the needs of orthopedic surgery. The robot can assist doctors to complete the orthopedic surgery in the surgical planning and monitoring, the path following, virtual fixture constraining, and so on, which lets the doctor feels that the robot is just a free surgical tool under the security operation.At first, the lightweight 6-DOF robot arm was modeled and analyzed systematically in the paper, which provided the basic kinematics data for human-robot interaction method and control of the orthopedic surgery robot. Including robot modeling based on D-H matrix, forward and inverse kinematics solution, velocity transformation through Jacobi matrix, which obtains the transformation relationships between the robot end position, velocity and joint angle, velocity. On the basis of the motion analysis, Monte Carlo method was applied to draw the working space of the robot, and the condition number of Jacobin matrix is used to retrieve singular points in the working space.On this basis, the proposed human-robot interaction method was implemented through the admittance control method based on speed control and security strategy based on virtual fixture technology. In order to enhance the performance of speed change and interaction about the control system, the three-level admittance gain parameter model based on admittance control was established. According to the characteristics of the orthopedic surgery, the guided and forbidden virtual fixture model were established, therefore the research of surgical safety strategy and modeling method based on virtual fixture was completed.Then, according to the complex and high real-time requirements characteristic of the human-robot interaction, the control scheme of hardware and software based on the real-time control software Twin CAT and the industrial Ethernet bus communication Ether CAT was proposed and implemented. VC was applied to complete the control interface, real-time display, kinematics algorithms, collaborative interaction movement and the development of sensor integration algorithm. Besides, the design, selection, implementation, assembly, debug of hardware and software of the control system was completed, as well as the precision calibration of the robot.Finally, the validation platform of human-robot interaction was established. At first, control hardware and software of the system and the motion control function were tested,so as to verify the reliability of each part of the system. Based on admittance control algorithm, virtual fixture modeling method, a series of experiments of leading, positioning and obstacle avoiding on the characteristics of the orthopedic surgery have been completed, including target positioning, curve trace leading,active and passive deviating from the pass, together with the simulation experiment of joint replacement surgery. The experimental results show that the proposed interaction control method based on the admittance and virtual fixture has good control performance. |
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