ABSTRACT
This chapter presents the design and development of electromagnetic actuators for ventricular assist devices (VADs). In order to make a brief introduction, it is worth remembering that we can have pulsatile devices or continuous flow ventricular assist devices (CFVADs). As already described in the previous chapter on VAD design, an important part of the devices is the actuators, the energy converters. The most common actuators are pneumatic, electromechanical, or hydraulic, but it would be redundant to name two other classes as electropneumatic and electrohydraulic. Normally, this energy is converted from moving storage (batteries). With the quality of the modern batteries, their autonomy, and the current charge-to-weight ratio, even pulsatile devices use batteries. Therefore, a detailed description of different conceptions would be necessary to describe different approaches to actuators. To facilitate understanding, we decided to describe the most common actuator (used in both electromechanical pulsatile VADs and axial or centrifugal CFVADs), the brushless direct current (BLDC) motor. This actuator is an electromagnetic converter composed of groups of coils controlled by an electronic driver board that makes the switching by alternating the current between the coils. This BLDC normally drives the VAD rotors by means of permanent magnets coupled to the impeller, either directly or by means of an indirect magnetic coupling. The rotor of the VADs must be supported by magnetic levitation, or by pivot bearings. Let us start this chapter by describing a centrifugal VAD with ceramic bearings and the calculation process, computer numerical simulations, and the construction of an optimized BLDC electromechanical actuator.
