Dynamics Study of Electromechanical Actuator of an Implantable Centrifugal Blood Pump Using a Simulation State-space Model

The permanent magnet brushless direct current motor (BLDC), have been the main component in most of the Ventricular Assist Devices (VAD) development. An implantable centrifugal blood pump is being studied at the Institute Dante Pazzanese of Cardiology (IDPC) as Ventricular Assist Device (VAD) to assist patients with cardiovascular diseases. Its use in patients with heart disease is indicated as a bridge to cardiac transplantation, as a bridge to the patient's recovery and as a bridge for gene therapy. Among the characteristics of the BLDC motors used in implantable pumps, there is the absence of brushes, which allows avoiding the inevitable detrition observed in other motors, and intolerable in VAD’s. Thus, improvements can be studied in the motor controller and they are required to obtain a reliable dynamic model. Toolbox SimPowerSystems software package (SimPowerSystems, MATLAB, Simulink) was used to study the dynamic system. The electromagnetic and mechanical parts of the motor were represented by a block Permant Magnet Synchronous Machine (PMSM) with a trapezoidal Back Electromotive Force (BEMF) signal. The block implements the differential equations for the motor through a state-space model. A Proportional Integral controller (PI) was used for the simulations. Electromagnetic and mechanical parameters were proposed in simulations that showed satisfactory results when compared with results of tests conducted earlier in the actuator. In future works, the results presented in this work will be used to refine the motor model for this application. Thus, it will allow reliable simulations of new proposed drivers.