# Physiological Control Law for Rotary Blood Pumps with Full-State Feedback Method
## 4 Discussion  
Naturally, as the VAD and the controller are implanted in humans, because their lifespan depends largely on the suitability of the pump control, we must have great certainty in the robustness of the control algorithms [29; 30]. Continuous flow for VADs may allow simulated pulses; however, until the  
Figure 11: Pump flow pulsatility vs average pulsatile flow at the transition from rest to exercise. Figure 10: Flow rate for systematic and pulmonary at the transition from rest to exercise. date of circulatory assistance, despite tolerance to left ventricular and Pao, the continuous flow rate is traditionally of a medium constant rotation, which always decreases the pressure pulse [31; 32]. These types of devices generally require precise control and the use of sensors to measure flow and pressure. These devices are not reliable, owing to clinical issues such as routine calibration and blood clotting [8]. These concerns regarding the reliability of implantable sensors have led to the search for non-invasive, sensorless approaches to identifying analog cardiac preload. We now believe that non-invasive technology has advanced to a level where it can be considered for long-term implantation, combined with sensorless signals, to form a robust control system that provides physiological behavior to RBPs [9]. The pulsatile flow pump is used as a non-invasive substitute for the LV filling pressure, as it has been proven to be closely interrelated. The pump flow pulsation and mean flow pump used in the current controller can be estimated using an algorithm for flow estimation previously established in our laboratory using the pump speed and current that are not measured invasively. The current control approach uses flow pulsatility as a parameter to determine the required flow rate compared to the continuous pulsatility index (PI) control strategy, which regulates PI directly at a specific stage. This allows the left ventricle to automatically adjust the RV output (represented by the increased or decreased pump pulsatility), thereby decreasing the danger of suction or an inefficient pumping aid connected to improperly defined PI target values. The optimal target PI value depends on heart contractility, preload, and afterload [18]. The methodology of this work is proposed to evaluate the merits of a full-state feedback control method involving sensorless and non-invasive approaches in a range of identical simulation scenarios. The results of this method show that the controller has advantages in regulating the reference signal generated with the safe mode at a variable speed, as illustrated in Figures 4-11. The software simulation model currently simulates rest and exercise with changes in HR, cardiac contractility, and systemic vascular resistance. Clinically, it is observed that large changes in pump pulsatility during postural changes cause patients to sometimes feel weak during Valsalva maneuvers (e.g., when coughing or straining) [33]. Therefore, we believe it is important to improve the software model to represent these events. In addition, the aortic valve is observed to be closed in most LVAD patients. However, with a change in posture, cardiac recovery, and during exercise, it may open. We have found that the aortic valve offers a lower resistance pathway than the LVAD bypass route, as the native heart sometimes pumps a significant flow relative to that of the LVAD. Therefore, we believe that this different pumping state could greatly impact our overall control strategy, and therefore requires online detection. In addition, during use in a clinical setting, it was found that controlling the pulsatility index to a pre-set point did not prevent antagonistic pumping states. On the contrary, occasional suction occurred, which led to the development of algorithms for anti-suction [34; 35]. Another drawback is that the pulsatility index (PI) is increasingly dependent on heart rate [36].