Vibration Reduction On Robotic Assisted Femoral Bone Drilling Using Soft Damper

Bone drilling is an essential part of many orthopedic surgical procedures,for both minimally invasive surgery,bone internal fixation and for attaching prosthetics.The success of any surgical drilling is a factor depending on the skill of the surgeon,the precision and accuracy especially when drilling of the femoral bone.Large forces and vibrations experienced during bone drilling causes crack formation and can result in drill overrun or breakage,causing considerable damage to surrounding tissues and result to severe complications.Therefore,it is important to understand the effect of high bone drilling forces and vibration during surgical drilling of bone,the aim of this research was to study how the cutting forces and vibration can be controlled during surgical drilling of femoral shaft by developing a method of vibration control applicable to the surgical drill,using HANS ROBOT.This research work also cover the experimental modeling,mechanical analysis and comparative analysis of three different fractured bone samples by drilling and implantation,with a high consideration for measurement of forces,torque and vibration control in all the samples.The stiffness of the robot was also considered during this experiment in order to accurately manipulate drilling operation,the accuracy and the rigidity needed by the force effector to drill with less vibration and deflections was considered.This practical experimentation also provide a control to excessive vibration on the femur bone which is based on the collection and analysis of the data obtained during drilling while varying the parameters such as pressures in the balloon,drilling speed and specified depth of cut.The amount of vibration caused by drilling forces acting on the bone at varying damper pressure and spindle speed was obtained using(EMS 309)data acquisition and amplified,then imported from excel to MATLAB R2015 b to analyzed our results and then compared with vibration results obtained when the bone was not damped with soft clamp.The outcome of the analytical study of the dynamic model was also verified.The vibration characteristic of the simulated bone and the drill was also modeled using ANSYS software to detect the amount of deformations,stress and strain in the bone while drilling.This experimental concept was also performed to predict,investigate,measure and compare the proportional relationship of the vibration frequency and cutting force with temperature rise during robotic assisted drilling of bone in order to avert possible damage due to high vibration.Finite element modeling of the bone was also done to determine force,stress and temperature data on the drilled bone.Therefore,this concept can be to predict surgical bone drilling result,high frequency of vibration is a menace that needed to be considered in bone drilling.This confirms the effectiveness of using drilling data as a forecast of bone extreme forces and vibration.In this research,a robot was designed to adequately measure the force,torque and to damp the vibration using a controlled soft air damper.The drilling force were measured by force sensor and accelerometer,since in an ideal situation the vibration amplitude of the bone is proportional to the increase in the cutting force,but due to adequate clamping and damping of the system,the amount of vibration were minimized.The balloon force and pressure was modeled and the resulted vibration signals were filtered by applying Fast Fourier Transform(FFT)from the beginning to the end of the drilling process,with detail magnitude plot and phase plot of the balloon damped vibration signal at varying robot spindle speed,results obtained was compared with both damped and un-damped situation.The main outcome of this thesis is a comprehensive experimental and numerical modal analysis of drilling forces and vibration,its reduction at different cutting speed and with a change in the pressure of the balloon damper,which prove the efficacy of using soft damper system to reduce force and vibration,adopting drilling system model developed.