| Recently,Natural Orifice Transluminal Endoscopic Surgery(NOTES)has become the focus of surgeons and scholars gradually,due to its advantages of no trauma,less bleeding and short recovery time.To accommodate the flexibility of the human orifice,the configuration of the surgical instruments for NOTES has switched into slender snake-like structure.However,there still exist issues in practical use,such as discomfort of patients or orifice injury during the insertion of instrument,and the difficulty in forming an effective triangulation at the end of instrument.This paper creatively proposed solutions to the above problems based on the concept of variable configuration.The main research results are as follows:To address the problem that the insertion of NOTES instruments may easily cause discomfort of patients,this paper proposed a new design for the main part of the instrument with radial variable configuration and the corresponding operation mode.The main part takes the Bricard mechanisms as deployable units,which allow the instrument to enter the human orifice in small scale and achieve a wide range of dimension change through simple actuation.On this basis,the key parameters of the Bricard mechanism were optimized and the motion continuity analysis was completed.At the same time,the relevance between the layout of the internal restoring force of the deployable unit and the motion interference was deeply explored.The kinematic description of the folding and deploying process of the unit was also completed,which can be used to precisely control the dimension of the instrument.In order to realize the actuation of multiple deployable units,three designs of actuation mechanism were proposed.The driving force equations were established respectively by using the principle of virtual work.Meanwhile,the key parameters of the mechanism were extracted and the optimal geometric parameters were acquired with the goal of minimizing the driving force.The relevant experimental verification was carried out likewise.On this basis,the whole mechanism was decomposed and equations of its internal forces were established.The stress distribution map of the Bricard linkage was drawn with the ANSYS software.Finally,the specific configuration of the linkage was re-optimized to reduce the stress concentration of the mechanism in the process of movement.To realize the sufficient deployment of the triangulation at the end of the instrument,a pneumatic variable-configuration structure combining soft structure and origami was proposed.Compared with the traditional deployable mechanism for triangulation,the new structure responds faster with a larger deployable range and has a flexible adaptability to the surrounding environment.The deformation of the structure was simulated by ABAQUS software.Based on this,a kind of hollow origami skeleton was proposed to reduce the volume expansion rate at the same bending angle.In addition,a soft origami model was made to preliminarily validate the deformation effect of the proposed structure.Based on the above research,this study carried out detailed experimental verification of the actual application effect of the proposed variable-configuration instrument.Simulative insertion experiment was designed to quantitatively describe the attenuating effect of the instrument main part on the shear force and normal force to the cavity.Through ex-vivo experiment for damage assessment of esophageal tissue,the morphological changes of the inner wall of the orifice before and after operation were demonstrated from a biological point of view.Finally,the performance test of the soft origami structure was finished,which verified the feasibility of the method to realize effective triangulation and the application potential in future NOTES surgery. |
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