Research On Optimizaiton Design And Control Method Of Gastrointestinal Surgery Robot

Gastrointestinal(GI)cancer includes colorectal cancer,gastric cancer,esophageal cancer,etc.According to data from the National Cancer Center of China in 2022,GI cancer accounts for approximately 26%of all cancer incidence and has become the leading cause of death that threatens human life and health in China.Taking colorectal cancer as an example,the 5-year survival rate after early surgery can reach up to 90%,with only 14%in advanced stages.Therefore,the key to improving patient survival rate is to use endoscopic minimally invasive surgery(MIS)for early diagnosis and treatment of tumors.The MIS of the GI tract has many advantages,such as less bleeding during surgery,low risk of postoperative infection,and no scars on the body surface after surgery.It has become the preferred treatment for early GI cancer by many patients and medical practitioners.However,due to the narrow,winding,and lengthy cavity characteristics of the GI tract,the application of high-degree-of-freedom manipulators and high-stiffness transmission mechanisms is limited.This leads to that the current GI surgical robots(GSRs)still have many problems such as low loading capacity,poor dexterity,and large tracking errors.Based on the analysis of clinical requirements,the innovative corresponding solutions are proposed in this dissertation as follows.1.Based on the requirements of MIS for robot dexterity,compliance,and robustness,and the collaboration requirements of robot modules,the optimization and design of the manipulator,endoscope and control system are innovatively carried out.This lays the foundation for robots to perform complex operations in narrow lumen.Based on the narrow,long,and curved biological characteristics of digestive tracts,the overall design requirements of the robot such as dexterity,section diameter,compliance and workspace are determined.To address the issues of uneven stress distribution and insufficient load capacity of microsurgery manipulators for narrow digestive tracts,a cable-stayed continuum manipulator with tube cutting mechanism and its optimization method are proposed.This achieves the design goals of integrating rigidity and flexibility,uniformly distributed stress,and optimal load capacity for the manipulator.A four-wire independently driven rolling-joint endoscope and its driving mechanism are designed to meet the requirements of endoscopic applications with strong load,sufficient space,dexterity,and flexibility.The comprehensive planning and design of the surgical-robot control system is carried out.The design goals of interface compatibility between the functional modules,convenient debugging,and circuit simplification are realized.2.To address the issues of sudden changes in joint trajectory and difficulty in constructing the surgical triangle under the master-slave mapping control of surgical robots,joint trajectory smoothing transition algorithm and endoscope channel angle optimization algorithm are proposed.This achieves coordinated and dexterous operation of both manipulators under the master-slave pseudo-Cartesian mapping control.The inverse kinematics transcendental equations for the manipulator are solved using linear regression analysis.Accurate kinematic modeling of the endoscope and surgical manipulator is completed.To address the issue of small distance,easy interference,and poor coordination in dual-arm cooperation,a method is proposed for optimizing the endoscope instrument channel angle under the combined constraints of dual-arm collaborative space and instrument end poses.This eliminates the chopstick effect of the double-arm cooperation and completes the construction of the surgical triangle.A sigmoid curve smoothing algorithm is proposed to address the issue of sudden changes in joint trajectory at the singularity.This enables the manipulator to pass through the singularity smoothly,and meet the requirement for smooth motion of the manipulator during surgery.3.To solve the problems of poor tracking accuracy,high hysteresis,and difficult sensing of the surgical manipulator,a feedforward compensation control method and a load force estimation method for the manipulator are proposed.This realize motion error compensation and sensorless force estimation of the manipulator.Friction modeling of the tendon-sheath transmission mechanism of the manipulator is carried out by using the microelement method.An elastic elongation model of the tendon is established based on the friction model.A friction feedforward-based motion compensation method is proposed by combining the tendon elongation model and the manipulator kinematics model.Based on the neural network training,the static model of the manipulator is obtained.By combining the static model of the manipulator with the tendon-sheath friction model,a sensorless method for estimating the load of the manipulator is proposed.The load force estimation experiments show that the load force estimation accuracy of the proposed method can meet the application requirements.Trajectory tracking experiments show that feedforward compensation control can double the tracking accuracy of the manipulator.4.To solve the problems of large tracking error and high hysteresis caused by the lack of feedback control of the surgical manipulator,a generalized proportional integral observer(GPIO)based sliding mode controller(SMC)for the manipulator is designed.This enables robust tracking of the manipulator under lumped disturbance compensation.According to the structure and force characteristics of the manipulator,the energy and generalized force during surgical manipulator motion are analyzed.The dynamic model of the surgical manipulator is established based on the Lagrangian dynamic formula.It is verified by simulation and experiment.According to the dynamic model of the manipulator,a reaching law-based SMC is designed.To realize the compensation of the disturbance which are difficult to measure in the system,the GPIO for the lumped disturbance of the system is designed.The simulation and experimental results show that the GPIO-based SMC can make the system converge within a limited time,while it has better robustness and better control effect than the feedforward compensation control.5.Based on mechanism design optimization and algorithm simulation experiments,system integration and comprehensive experimental verification of GSR are completed.Experiments on the bending angle,load capacity,and trajectory tracking of the endoscope are carried out.The results showed that the endoscope designed in this work can provide strong support for the operation in terms of flexible field of view,high load capacity,and precise positioning.The experiments for manipulator degree-of-freedom(DOF),clamping force,and master-slave labeling are also conducted.The results showed that the dexterity,clamping force,and tracking accuracy of the manipulator all meet the design requirements.Experiments on clamping,puncture,and isolated tissue-cutting by the surgical robots were carried out.The results showed that the surgical robot system developed in this work has the potential to be applied to gastrointestinal MIS.