Control system design for external continuous flow centrifugal VAD

Abstract

Ventricular assist device (VAD) is used in heart failure patient. VAD works instead of heart function. The disadvantage of current VAD is a constant pump speed that is manually adjusted. However, the constant of pump speed is not providing the constant of pump flow. Therefore, the flow control or manually adjust is an important for maintain blood circulation in patient. In this research, the automatic system that can maintain both pump flow and head pressure (arterial blood pressure related) was developed by using control system method, so it makes the patient be safe from abnormal symptom. In hardware part, the flow rate was collected by the ultrasonic flow sensor and the head pressure was collected by the fluid fill pressure sensor. All signals were transmitted to microcontroller for analog to digital conversion. A microcontroller was programed with the control algorithm. Microcontroller controls the input power of VAD's motor that related to VAD speed. Personal computer was used as control panel and display. For control system part, Fuzzy Logic control was used as control algorithm. The system maintains the flow rate or head pressure. The system was tested on mock circulation loop. The mock circulation loop simulates the condition of body circulatory system. After tuning and improvement of controller, both pump flow and head pressure can be maintained. However, the time-response was not spontaneously after the outflow pressure has changed. The pressure response has high overshoot when systemic resistance increases. The flow rate response has high settling time when the systemic resistance has increases. Therefore, the control algorithm needs to improve for reducing both the pump flow and head pressure responses.