# Physiological Control Law for Rotary Blood Pumps with Full-State Feedback Method
## 1 Introduction
In addition, a logical theory also suggests that recirculation events may occur inside the left ventricle, which is the result of changes in the natural direction of blood flow combined with the decreased movement of the left ventricle wall due to excessive unloading [13]. Currently, there is only limited evidence of thrombus formation in the left ventricle. However, atrial fibrillation may occur in the case of excess unloading of the left ventricle. In this case, thromboembolic complications are common [14]. Complete left ventricular unloading is only considered in those patients believed to have a greater chance of recovery from cardiac assist devices, or those patients eligible for weaning [15]. The preceding points clearly show that it is not always a good decision to operate the rotary blood pump at its peak flow rate. Instead, it is preferable to operate it at a point where the unloading is only done halfway. Thus, the left ventricular volume and the left ventricular wall movement are not restricted, and the left ventricular cavity is at an ideal achievable washout where the occasional opening of the aortic valve also occurs [16]. With this in mind, it is important to note that there is a constant need for a physician to monitor the control method, in terms of adjusting the point at which it operates, regardless of the physiological situation. Such a point chosen for operation may be directly dependent on the therapeutic objectives, such as those being discussed. Moreover, therapeutic devices can also be divided into the following two categories: full assist (FA) devices, which guarantee extreme support with a sealed aortic valve and a margin for safety measures, and partial assist (PA) devices, which offer partial support in the region, where events related to the permanent opening and closing of the aortic valve occur. In addition, in the latter case, the transition occurs with an improved left ventricular washout and moderate left ventricular loading, while the volume of the left ventricle is the most physiologically close as possible [16]. One of the most obvious challenges of the existing control strategies is the various levels of heart failure that need to be addressed. These levels can range from the degrading function of the ventricles, usually without pulsation, to the proper functioning of the ventricles with adequate aortic flow [17]. Some researchers initially claimed, as seen in the literature review, that a constant pressure differential combined with a fixed average speed was appropriate when considering getting used to the different preload levels. However, some researchers claim that rotary pump devices are insensitive to preload. The statement essentially implies that additional sensors are needed for these systems to duplicate a natural Frank-Starling behavior [18]. Each LVAD requires a technique for controlling the implantable LVAD, regardless of the type of control approach involved. This control is essentially responsible for adjusting the speed and flow rate, to keep the heart functioning under artificial conditions as close as possible to its natural physiological functioning. Thus, some control methods make use of the motor current consumption, as reported by [PERSON] et al. [19]. Using the motor current consumption is a method that can increase the life of the implantable ventricular assist device. This is essential, because the pump itself has the function of a sensor. In addition, it is also important to note that even the pulsatility of the human heart in its natural working form has the role of influencing the waveform of the motor current [19]. Considering all of these observations, it was comparatively easier to estimate the heart rate in its natural physiological working environment, and, in turn, it was also convenient to predict and treat ventricular collapse [20]. However, despite this, the level of control needed for a pulsatile ventricular assist device, better known as a total artificial heart, has not yet been achieved [21].