Research On Cable Transmission Characteristics And Estimation Of Grasping Force In Miniature Laparoscope Surgical Robot

In recent years,the Miniature Minimally Invasive Surgery Robots(MMISRs)with the advantages of integration,miniaturization and portability of have draw widely attention in the field of medical robots.Compared with the bulky and expensive abdominal minimally invasive surgical robots,the MMISRs have the advantages of small size,low cost and low price,which gives them research and application value.Some significant breakthroughs are made in key technologies of MMISR,but there are some difficulties and challenges in accuracy and real-time control of the MMISR due to the complex structure and hysteretic characteristics of the cable-pulley system in the end-effector.Aiming at the challenges of transmission characteristics of the cable-pulley system,this dissertation presents the researches focusing on transmission characteristics modelling of the cable-pulley system,estimation of grasping force and design of the integrated tension sensing measurement system for the MMISR.In order to address the challenges of large position tracking errors of the end-effector caused by hysteretic characteristics of cable-pulley system,the transmission characteristic model of the cable-pulley system is built.The routes of the cable-pulley system are designed,and the force of the infinitesimal cable is analyzed,which is used to model the transmission characteristics of the cable-pulley system.In the model,the bending rigidity of the cable is considered.The tension loss of the cable is analyzed.The static and dynamic transmission characteristics experiments are developed to valid the tension loss.Based on the transmission characteristics of the single cable-pulley system,the model of cable-pulley system of the end-effector is developed.In order to address the challenges of estimation of the grasping force of the endeffector,a method of estimation based on the model of the cable-pulley system is proposed.The friction loss between two adjacent pulleys is analyzed.The coupled characteristics between pitch and yaw motion of the end-effector are studied and validated by the experiments.Considering the friction loss and the coupled characteristics,the grasping force is estimated based on the model of cable-pulley system of the end-effector.The results of experiments validated the method of estimation.The method can be used to estimate the grasping force while the force sensor is located in driving unit side of the end-effector.In order to address the problem that the force sensor is not installed and integrated in the end-effector,an integrated tension sensing measurement system based on the fiber Bragg gratings(FBGs)is designed,which is mounted on the side of the driving unit of the MMISR.The measurement system is calibrated and tested by the experiments.The results of the experiments show that the integrated tension sensing measurement system has good linearity.In order to compare with commercial miniature tension sensors,the experiments are performed.The results of the experiments show that the measurement system assembled in the cable-pulley system can be satisfied for the application requirements of the MMISR.The measurement system,which is used to estimate the grasping force of the end-effector,is easy to install and integrate and avoids the electromagnetic interference(EMI)and high temperature disinfection process.In order to verify the transmission characteristics of the cable-pulley system and the method of grasping force estimation using the proposed measurement system,a MMISR is designed.The MMISR uses a position compensation algorithm which is proposed and used to improve tracking accuracy of the end-effector.The results of experiments show that the algorithm is capable of improving the position tracking performance.Meanwhile,it verify the validity of the transmission characteristics of the cable-pulley system.In order to estimate the grasping force of the end-effector,the integrated tension sensing measurement system is installed in the MISR.Based on the proposed grasping force estimation method,the experiments verified the validation of the measurement system proposed.In order to verify the feasibility of clinical application of the MMISR,the training experiments on laparoscope simulator and animal clinical experiments are performed.The results of the experiments show that the MMISR developed has a stable and ample grasping force,good operability and flexibility,high clinical application value and broad application prospects.