Simulation And Experimental Study Of A Biventricular Assist System Based On SL-SMC Combined Controller

For most patients with end-stage biventricular failure,implantation of a biventricular assist device is an effective treatment.The ventricular assist device helps the failing heart to pump blood and keeps the patient alive by varying the rate of rotation.However,the device has a low preload sensitivity and high afterload sensitivity compared to the natural heart,and has difficulty balancing systemic blood flow,underperfusion and ventricular suction during the assist process.To solve these problems,this paper proposes a combined SL-SMC controller suitable for biventricular assist devices by combining the Starling-Like controller,which simulates the natural heart’s pumping mechanism,and the Sliding Mode Controller(SMC)with a fast response.Both simulation and experimental research on the biventricular assist system using this controller have been are carried out.The main contents are as follows.Firstly,the lumped parameter model of the biventricular assist system is developed.The lumped parameter model of the biventricular circulatory system is first proposed by analogy of cardiovascular mechanical and electrical parameters.A biventricular circulation model is built in Simulink,numerical simulations are performed for both physiological states of heart failure and health,and the main hemodynamic parameters were compared with literature and clinical data to validate the model.Then,the left and right ventricular assist device models are established and coupled to the biventricular circulation system to develop the lumped parameter model of the biventricular assist system for evaluating the control performance of the combined SL-SMC controller.Secondly,a combined SL-SMC control strategy is proposed to balance systemic blood flow,prevent ventricular tamponade and meet the perfusion requirements of different physiological states.Based on the biventricular assisted circulatory system,the control performance of the combined SL-SMC controller is evaluated in both the elevated pulmonary resistance test and the resting exercise test,with the combined SL-PI controller and constant velocity controller as control groups.The results show that in these two sets of experiments,the combined SL-SMC controller can effectively balance the blood flow,avoid left ventricular suction,and achieve higher cardiac output,and it also demonstrates a stronger response speed and immunity than the PI controller.Then,an adaptive mechanism is introduced to the combined SL-SMC controller to decrease the risk of right ventricular suction and perfusion capability of the system at the exercise state.The results show that the combined SL-SMC controller with the adaptive mechanism can avoid the risk of right ventricular suction in the elevated pulmonary artery resistance experiment and provide higher cardiac output in the resting-exercise experiment than the combined SL-SMC controller without the adaptive mechanism.Finally,a biventricular circulation experimental platform that can simulate human blood circulation was developed to carry out experimental research on the biventricular assist system based on the combined controller.With Lab VIEW as the development platform and data acquisition card as the acquisition and output basis,the pressure and flow acquisition system to achieve real-time data acquisition and the driving system for ventricular assist device.Experiments with increased pulmonary artery resistance and resting exercise were performed for the SL-SMC combination controller,and the results were consistent with the conclusions from the simulations.The experimental studies showed that the biventricular assist system using the SL-SMC combination controller performed better overall than the SL-PI combination controller and constant velocity control in terms of balancing systemic blood flow,avoiding ventricular tamponade,improving physiological perfusion and speed of response.