Design And Analysis Of Passive Posture Adjusting Mechanism Of Transrectal Ultrasound Probe

With the development of robotics and computer imaging technology,minimally invasive surgery has made great progress and applied in the clinic surgery more and more.However,the existing active prostate interventional robot is difficult to popularize because of its complex system,high cost,and the long training time.In view of this,the paper designs a passive posture adjustment mechanism of ultrasonic probe for transrectal prostate biopsy,used to assist doctors to complete the surgery for the diagnosis of prostate cancer,this mechanism can not only enhance the efficiency,accuracy and security of the operation,but also reduce the pain of patients,the workload of doctors and the cost of application.The procedure of transrectal prostate biopsy guided by ultrasound is analyzed,and based on this,the design requirements of ultrasonic probe posture adjustment mechanism are put forward.The position adjustment module that can interlock four joint at the same time is designed through the analysis of the contradiction matrix and invention principle,the linkage size is optimized by using two-sequence optimization algorithm to meet the optimal size of working space under the operation demand.The posture adjustment module that enables the ultrasonic probe to realize remote centering function by using a double parallel quadrangular remote center mechanism,so as to prevent the radial jump of the ultrasonic probe in the operation.The ultrasonic probe autorotation and feed module designed by C type structure are easy to install the ultrasonic probe and biopsy gun frame,6 independently distributed rubber blocks can be used to clamp the irregular shape of ultrasonic probe.The reachable workspace of the mechanism is solved in Matlab software,the corresponding position relationship between the reachable workspace and the operation demand workspace is obtained,results show that the reachable workspace can meet the operation requirements,the centering effect of the ultrasonic probe at different feeding distances was simulated,and the results showed that the ultrasonic probe was stable.The stiffness and strength analysis of the two positions of the mechanism at the most distal and the nearest end are carried out by ANSYS under self-weight and interference load,the results show that the deformation of the whole mechanism to meet the operation requirements,the maximum equivalent stress is far less than the material allowable stress,the safety performance of the mechanism is verified.The physical prototype of passive posture adjusting mechanism of transrectal ultrasound probe is developed in this paper,the continuous motion range and locking force of the joints and the required driving force when the joint in the relaxation state are measured,verified that the mechanism could reach the required operating space at any location flexibly,and the locking position is reliable.The static stiffness of the mechanism in the case of different attitude is measured in the case of self-weight,the displacement of remote center point relative to the theoretical coordinate point is obtained,results show that the displacement can meet the requirements of the operation and provide the basis for the error compensation of the doctor's operating.The centering effect of the distal center of the ultrasonic probe was measured in the actual operation,the displacement range of the far center point in the space is obtained,results show that the centering effect of the ultrasonic probe is stable,and the passive posture adjusting mechanism of transrectal ultrasound probe can meet the requirements of the operation.