The study of the piston driving and position sensing for a linearly moving piston pump

The major component of the left ventricular assist device (LVAD) is the pump and the pulsatile pump can generate the pulsatile flow which is similar to the circulation human body. In this research work, the control method of the piston movement for a linearly moving piston pump has been developed. The pump owned 24-sets coils outside the tube and a piston inlaid with a permanent magnet was inside. An induced magnetic field was interact to the magnet and generated repulsive or attractive force to drive the piston when the current was applied to the coil. Some simulation of the magnetic field distribution with different numbers of coils carrying the different direction current has been done. To verify the simulation and the real situation of the piston moving, the Hall Effect sensors were used to sense the piston. The sensing signals showed the piston moved smoothly and controllable in the air under attractive force. However, the combination of repulsive or attractive forces was needed when the water was pumped in a simple channel by it. The flow rate was about 5.5 liters per minute when the pump was connected to the blood circulation simulation machine provided by Keelung Chang Gung Memorial Hospital. The developed control signals was successful to drive the linearly moving piston pump and achieve the minimum required flow rate for a LVAD.