Design Of A Soft Continuum Robot For Pulmonary Intervention

Early diagnosis of lung cancer is crucial to improve the survival rate of lung cancer patients.Among the early diagnosis modalities of lung cancer,intrabronchial intervention biopsy is the least invasive modality.However,the existing bronchoscope intervention has disadvantages such as lack of operation flexibility,insufficient depth of intervention,and poor accuracy.This article focuses on the research work of a soft continuum robot applied to lung bronchial intervention biopsy surgery,including structural design and construction,mixed kinematic modeling,and experimental verification.The main research contents are as follows:To meet the requirements of intrabronchial intervention biopsy,a rope-driven soft continuum robot with multiple degrees of freedom was designed,mainly composed of a two-segment soft continuum manipulator,a bending guide drive module,and a linear push drive module.The rope drive achieves separation of in vivo execution and external drive,and the two-segment manipulator improves the flexibility of the continuum robot.The soft continuum manipulator is a notched flexible skeleton and rope guide disc structure with small scale outer diameter,large inner diameter working channel and full dimensional large angle bending performance.The bending drive module can control the full-dimensional guiding motion of the two-segment soft continuum manipulator through the driving rope,and the linear push drive module can control the linear reciprocating motion of the two-segment soft continuum manipulator through synchronous belt transmission.To solve the problem of motion control accuracy of the rope-driven multi-segment continuum manipulator,and based on the configuration of the continuum manipulator,the mapping relationship between the driving space,configuration space,and task space was established,and a hybrid kinematic model with error compensation was constructed.The forward and inverse kinematic models between the task space and configuration space were established by using the segmented constant curvature and particle swarm algorithm,and kinematic simulation and workspace accessibility analysis were performed.Based on the control method of human mixed decision-making in the environment,an incremental mapping based on the configuration space was established.To solve the problem that the nonlinear error of the continuum manipulator is complex to establish an accurate model,a particle swarm optimization-based back propagation neural network error compensation model and a multi-segment decoupling model were proposed to form a hybrid kinematic model,and the kinematic mapping relationship between the configuration space and the driving space was established.The nonlinear mapping relationship between the joint angle of the continuum manipulator and the stretching compensation of the driving rope was fitted,improving the motion control accuracy of the continuum robot.To verify the flexibility of the proposed continuum robot and the effectiveness of the kinematic model,an experimental platform was constructed.A bending guide experiment,a trajectory tracking comparison experiment,and simulated continuum robot intervention bronchial model experiment were set up.The bending guide experiment verified that the soft continuum mechanical has the flexibility of multi-directional rotation and 180° large-angle bending.The results of the trajectory tracking comparison experiment verified that the hybrid kinematic model with error compensation outperformed the segmented decoupling constant curvature kinematic model,and the average absolute error was reduced by about 60% when a single-segment continuum manipulator moved,and the average absolute error was reduced by about 70% when a two-segment continuum manipulator moved.The simulated continuum robot intervention bronchial model experiments showed that the continuum robot can collect lesion samples in the apical branch of the right superior lobe bronchial apical segment which is more difficult to intervene clinically,the medial branch of the right middle lobe bronchial lateral segment,the lateral branch of the right middle lobe bronchial medial segment,and the medial branch of the left lower lobe bronchial posterior basal segment,where the interventional distance is far.This experiment comprehensively assessed the feasibility of the continuum robot in the lung bronchial model application scenario.