Design Optimization And Control For Mechanical Left Ventricular Assistant Device

Heart is one of the most important organs in human body.Once pulsation stopped,life would come to an end.Heart failure is a major threat to mankind’s life.Artificial heart which integrates mechanical,electronical,fluidic and biological technology is an important way to save and improve the quality of life.Along with the deepening of studies on artificial heat,engineers are faced with new challenges on bionic structure design,fluid domain optimization,decreasing the domain of high shear stress and improving the pulsation performance of continuous flow LVADs.Decreasing the destruction to blood cells and providing the bionic pulsatile bood flow to circulation system is the key technology to the R&D of artificial heart.Designing the interior structure of artificial hearts to simulate the flow field of the natural heart,minimizing the high shear stress area in the artificial heart to decrease the damage to blood,improving the pulsation of left ventricular assist device to the greatest extent to simulate the natural heart for better terminal organ perfusion are hot issues for current studies.This paper carries out researches in the following three aspects for the problems mentioned above.1.Searching for the LVAD structure which could generate the flow filed similar to that in natural heart.Conducting numerical simulations of the designed geometrical structure to find the ideal structure and validating the simulation results by PIV experiments,simultaneously having comparison with the flow field within the natural heart.2.Working out the high shear stress volume of the centrifugal LVAD by numerical simulation and optimizing the rotary domain outline of centrifugal LVAD by response surface method,in order to minimize the high shear stress area’s damage to blood cells.3.Building up the lumped parameter model of the circulation system coupling with model of artificial heart pump as well as validating the effectiveness of the model;controlling mean arterial pressure to deal with various physiological changes;producing pulsatile pressure within the circulation system and using particle swarm optimization to obtain the maximum surplus hemodynamic energy.The following three main conclusions are obtained by this paper’s in-depth study on the aforementioned three issues:1.Through numerical simulation comparison among three structural design of LVAD,it is found when the structure of LVAD is similar to the bionic structure of the natural heart’s cardiovascular,the simulation results is mostly close to the vortex flow state in the natural heart during a pulsatile period.The numerical simulation results are also validated by the particle imaging experiments(PIV).Moreover,the artificial heat and natural heart have the same flow pattern.2.The geometries of centrifugal LVAD is built and Fluent is used to calculate the model.The rotary domain outline of the centrifugal LVAD is optimized by RSM.The domain of high shear stress is decreased by 20.7% in contrast to the average domain before optimization.3.The lumped parameter model of circulation system coupling with the model of artificial heart are built up in MATLAB.The effectiveness of the model is validated by comparing the model with the heart’s physiological parameter.A fuzzy controller is used to control the LVAD speed to maintain a normal physiological level of mean aortic pressure and adapt to a variety of physiological situations.The pulsation of the arterial pressure is realized through speed fluctuation of the LVAD.The maximum surplus hemodynamic energy is obtained by adjusting the phase and duty cycle of speed adjustment square wave with optimized particle swarm algorithm.This study has innovations in three aspects:1.This paper is the first one to propose to design the structure of pulsatile blood pump by structrual bionic theory.The bionic fluid domain is further realized on the base of structural bionic design.Continuous vortex flow which is similar to that in natural heart has been generated,which eliminated the vortex interruption and dissipation in previous pulsatile artificial heart design.2.The response surface method is applied to the rotational domain design of centrifugal LVAD for the first time.This considerably reduced high shear stress area in centrifugal LVAD for blood protection,which is in favor of the R&D of long-term LVAD.3.It’s the first one to search for the best combination of phase and duty cycle of speed adjustment square wave for maximum surplus hemodynamic energy with particle swarm optimization.Any surplus hemodynamic energy within the maximum hemodynamic energy range could be obtained in theory,which is conducive to the studies on recovery strategies of myocardium.