The Research Of Variable-diameter Bone Drilling System

Femoral head necrosis is a serious bone disease. The common treatment for this disease are drug therapy and surgery currently. The surgical treatment mainly uses drilling decompression surgery to keep the blood flowing recovery and release the pain, however, it will cause significant damage to the normal tissue which may need more time to recover. How to minimize trauma, shorten patient recovery, reduce patient suffering, is an important issue.This paper designs a variable-diameter bone drilling system. During the operation, drilling the femoral head with small diameter until reach the lesions area, the knives opened, then continue to drilling. It realized the purpose of reduce normal tissues trauma. The major work to the system is as follows:First, the mechanical structure design, including execution part, driving part, knives cutting part, scraps discharge and cooling section, and positioning work station. Execution part mainly realizes cutting and feeding function of the knives; Driving parts mainly provide tool the driving force of rotating, feeding and diameter changes; function of Scraps discharge and cooling is take away part of scraps; Positioning work station is to fix the position of the drilling machine, realizing three degrees of freedom movement.Second, the research of the control system. The system part include the control of the angle of knives, realize cutter diameter changing. The tension of the wire rope is measured by transducers and then transmitted to the single-chip microcomputer system. The processes of changing diameter and other movements are controlled by the main and implementation program. According to sensors, SCM, motor and other hardware design and choice.Third, the analysis and verification to the key parts using finite element method. The most important parts are the strength and stiffness of the cutting and drill pipe. According to the material and the external force status of the cutting and drill, the model is constructed and analyzed using ANSYS software; Because of the work load of the screw will be large, there is a certain degree of deflection, it must calculate the force screw maximum deflection, guarantee the deformation in the allowable range Inside, so the screw to check calculations.