Research On The Configuration Of Surgical Instruments Based On Topology Optimization

Minimally invasive surgery has the advantages of less bleeding from wounds,shorter recovery time,and smaller scar area.During minimally invasive surgery,surgical instruments are contact with human tissues directly.If the structure is designed unreasonably,it may cause irreversible damage to human tissues.When the surgical instrument arm passes through the human body cavity,the surgical instrument must provide sufficient degrees of freedom and flexibility;During precise operation stages such as stripping and traction,surgical instruments need to have higher rigidity and stability to maintain the stability of tissue operation.Therefore,improving the rigidity of the surgical instrument arm while maintaining the good flexibility of the surgical instrument is of great significance to the operation of minimally invasive surgery.In this thesis,the research object is the surgical instrument arm.The main research content includes the structural design,statics analysis,topology optimization and finite element analysis of surgical instrument arms,as well as the kinematics operation space and simulation analysis of surgical instruments.The specific content is as follows:（1）The research status of continuum robots and topology optimization methods are analyzed.First,the surgical operation process,degree of freedom,surgical operation force and surgical instrument configuration are explained in detail,and then the surgical instrument arm design goals of this thesis are formulated according to the requirements of size,working bending state,end load capacity,and material selection.Based on the design goal,an initial plan for a simple,2-degree-of-freedom bendable surgical instrument arm was proposed.（2）In-depth study of variable density topology optimization methods.A mathematical model with the minimum structural flexibility as the optimization objective function and the constraint function as the volume is constructed.The Lagrangian function is introduced,the mathematical model solving algorithm（optimization criterion algorithm）is deduced,and the iterative formula of the optimization criterion method based on SIMP theory is obtained.The numerical instability that often occurs in topology optimization and its solutions are discussed.Finally,taking a typical cantilever beam as an example,based on MATLAB software,the influence of the filter radius r and the penalty factor P on the topology result is discussed.（3）Topology optimization design for the initial scheme of the flexible surgical instrument arm.Based on the static analysis of the initial plan,the topology optimization method is introduced to improve its structure.Based on the results of topology optimization under different constraints,four new schemes are proposed.With the aid of finite element software,the maximum displacement and maximum stress change of the four schemes in the flexible and rigid working state of the surgical instrument are analyzed,and the better scheme is obtained by comparison.Optimize the size and shape of the final plan again,and compare the performance of the optimized structure with the original plan in this article.It is found that the stiffness performance of the optimized structure is increased by nearly 70%compared with the initial plan,and the maximum stress is reduced by nearly 54%,indicating that the optimized surgical instruments have better structural reliability,safety and service life.（4）Perform kinematics and end load simulation analysis on the surgical instrument arm.Since the surgical instrument arm designed in this thesis belongs to the category of continuum robots,the traditional D-H method cannot model its kinematics.Therefore,in this paper,the continuum structure is assumed to be a structure with virtual joints,based on the improved D-H method for theoretical modeling,and the configuration space between the minimally invasive surgical instrument arm’s configuration space-the working space and the driving space-the configuration space Mapping for research.Using MATLAB programming method,the end position of the surgical instrument arm was simulated and analyzed,and a curved work space similar to a three-dimensional coronal sphere was obtained.Analyzing the load-displacement change rule of the geometric center of the end of minimally invasive surgical instrument arms with different initial poses under the same load,verifying that the optimal structure designed meets the needs of surgery.