# An Advanced Physiological Control Algorithm for Left Ventricular Assist Devices
## 1 Introduction  
Heart failure (HF) is a disease that occurs when cardiac muscle exhibits an insufficient capacity to circulate blood adequately [1; 2]. A left ventricular assist device (LVAD) has emerged as a valuable solution to help patients suffering from this issue. Different studies have shown that an LVAD positively affects patient outcomes, including increased survival rates, symptom relief, and overall quality of life for individuals with advanced HF [3; 4; 5]. LVADs can significantly influence the physiology of the cardiovascular system (CVS) [6; 7]. As a result, one of the primary goals of enhancing the state of LVAD technology entails formulating a control approach that can adaptively regulate pump speed to accommodate differences in metabolic requirements [8; 9]. Therefore, the physiological control management of this type of device entails monitoring and adjusting device parameters to enhance its efficiency for a given patient. The main goal of LVAD treatment is to provide adequate assistance to the heart and maintain proper blood circulation throughout the body. Therefore, it is necessary to carefully observe the flow rate of the LVAD and determine the volume of blood circulated by the LVAD per unit of time. The LVAD flow rate is tailored to the patient's requirements and can be adjusted up or down to maintain optimal blood pressure and cardiac output. The aspiration inhibition system of LVADs is an essential physiological control parameter. Excessive suction from an LVAD can damage the heart muscle and cause the device to malfunction. The LVADs are equipped with suction prevention mechanisms that supervise intracardiac pressure levels and regulate the device flow rate accordingly to avoid undue suction [10; 11]. Various control techniques have been proposed for LVADs, including conventional PID controllers [12; 13], optimized controllers [14; 15; 16], sliding mode controllers [17; 18],H-infinity controllers based on the estimator model [19], fuzzy logic controllers [20; 21; 22], deadbeat controllers [23; 24], and predictive model controllers [25; 26; 27]. However, these methods may not be effective in dealing with the uncertainty and disturbances common in LVAD systems [28]. Recently, a model-free adaptive control technique has been used to regulate the speed of the LVAD pump in response to changes in the patient's CVS [29]. The methodology in this study designed an algorithm that calculates a coefficient of control over time and then uses existing data on the manipulated and control variables. The performance of this controller was evaluated and verified using computer simulations. The results indicate that LVAD can effectively adapt to changes in blood demand, whether constant or fluctuating. An alternative study presented a supervised adaptive fuzzy control approach featuring pulse-ratio modulation [30]. This study aimed to ensure adequate blood circulation perfusion and reduce the phenomena of aspiration. The results of this study indicate that implementing a supervised adaptive fuzzy controller can effectively prevent the system from experiencing suction hooking compared to conventional approaches. However, most adaptive control techniques suffer from the system convergence phenomenon of chatter, which causes stability convergence to slow down. Among the above techniques, an extremum-seeking control is a technique that attempts to determine the optimal value of the performance index by processing the control input of the LVAD. Recently, [PERSON] et al. [31] proposed a nonlinear controller that uses an extremum-seeking theory to regulate cardiac performance. The primary objective of the control unit was to improve the pump flow rate while at the same time minimizing the incidence of suction phenomena. An in silico model was used to evaluate the proposed controller, and the results indicate that it can effectively maintain an appropriate cardiac response. Moreover, it is observed that the mean arterial pressure remains within the required range, thus preventing aspiration.