SIMULATION STUDIES OF THE PENN STATE EVAD: VELOCITY CONTROL.

A mathematical model of the Penn State electric ventricular assist device (EVAD) motor is described. The circulatory load is simulated with a Windkessel with linear valves. The brushless dc motor is characterized by a back emf constant, torque constant, and resistance. This third-order model, with velocity, atrial pressure, and aortic pressure as state variables, was used in the design of a digital velocity control system. The system includes a double numerical integrator and a single-lead network. The plant and compensator combine to form a sixth-order model, which was tested using varying beat rates and initial conditions. Mean power was found not to depend strongly on the shape of the velocity profile. Good results were obtained with an ad hoc choice of initial conditions which depend on beat rate.