Research On Key Technologies Of Parameter Identification And Model Modification For Interventional Surgical Robots

Interventional surgery is a minimally invasive treatment in which surgeons use surgical instruments such as catheters and guidewires to diagnose and treat cardiovascular disease under X-rays.Teleoperation interventional surgical robot can assist doctors to complete the operation,so that doctors are far away from the radiation environment to avoid being exposed to X-ray radiation.At the same time,the surgical robot has good position and posture tracking performance,which can improve the accuracy of doctors’ operation of surgical instruments.However,the lack of force feedback information in the operation process is a problem faced by the teleoperation interventional surgical robot.In this paper,force feedback is taken as the research object,the motion control and force feedback control algorithm of master-slave surgical robot are discussed,the modeling method of catheter dynamics model and parameter identification algorithm are analyzed,and the model correction algorithm to improve the accuracy of force feedback calculation is studied.According to the way doctors push and twist the catheter,Omega.7 of the main end controller and UR5 of the slave end manipulator are selected to build the surgical robot platform.Considering the difference between the parallel structure of Omega.7 and the serial structure of UR5,starting from the coordinate system when Omega.7 and UR5 are used,the coordinate transformation mode is discussed,and the master-slave cooperative motion control method is proposed to ensure the accuracy of the position and posture tracking of the master-slave surgical robot.The force perception of the catheter "bouncing",the contact force perception threshold of the hand,and the delay between the master and slave systems are all the factors that affect the feedback control of the surgical robot.In this paper,sliding mode control is proposed as a force feedback control algorithm.According to the physical properties of the damping and stiffness coefficient of the flexible conduit,the sliding mode surface is designed,and the whole robustness of the system is improved by using the sliding mode controller.The key problem to be solved by master-slave surgical robot is how to accurately obtain the contact force when the catheter collides with the blood vessel.In this paper,the dynamic modeling of the main end of the pipe is carried out,and the mass-spring-damping model is proposed as the dynamic modeling method,so as to reflect the physical law of the pipe under the action of external force.Considering that the model parameters of catheter dynamics can’t be given accurately at the beginning,the model parameters should be obtained from the end identification.In this paper,the least square method is used as the parameter identification algorithm,and the objective function is designed according to the position and force data of the moving catheter,so as to obtain the accurate dynamic model parameters of the catheter.When the master end acquires the dynamics model of the slave end and modifies it,it will be affected by the time delay in the system,which requires the accuracy of force feedback calculation.In this paper,the generalized prediction algorithm is proposed to modify the dynamic model of the pipe.According to the identification parameters,the rolling optimization index function is designed to predict the model parameters at the current moment,so as to reduce the influence of time delay.Finally,the proposed algorithm was verified by experiments.A complete interventional surgical process of catheter pushing and twisting was carried out.The effectiveness and accuracy of the algorithm for the calculation of the main end feedback force were evaluated from three aspects: force feedback error,hand perception threshold and real-time force feedback.