# Adaptive Control of the Aerodynamic Flaps of the Savonius
## 1 Introduction  
Vertical-axis wind turbines (VAWTs) with Savonius rotors have gained increasing scientific attention in recent years due to their structural simplicity, low noise levels, ability to operate under weak and variable wind flows, and resilience to abrupt wind load changes. These turbines offer several advantages over their horizontal-axis counterparts, including omnidirectional wind capture, efficient operation at low wind speeds, no need for wind-direction alignment, and reduced operating costs. This makes them especially attractive for urban environments and remote areas [1]. Despite these advantages, Savonius-type VAWTs are characterized by relatively low wind energy conversion efficiency. A key research direction for improving their performance lies in the implementation of adaptive aerodynamic elements, such as controllable flaps. These components allow for real-time adjustment of aerodynamic drag and lift forces on the blades, thereby significantly improving the generator's performance across a wide range of wind conditions. Aerodynamic flaps mounted on Savonius rotor blades can optimize airflow around the blades and effectively control the torque generated by the wind [2]. This, in turn, helps to minimize mechanical stress on structural components, extending their service lifeand reducing maintenance costs. However, effective utilization of such flaps requires a sophisticated control system capable of rapidly and accurately responding to constantly changing external conditions, including sudden gusts and abrupt variations in wind direction and speed. Most existing flap control approaches rely on traditional controllers with fixed parameters, which demonstrate limited adaptability and insufficient responsiveness under real-world operational conditions [3]. These systems often fail to adequately compensate for dynamic disturbances and abrupt wind fluctuations, leading to decreased overall turbine performance and increased risk of mechanical damage. Research aimed at improving the efficiency of vertical-axis wind turbines (VAWTs) of the Savonius type has been actively evolving over the past decade, offering various approaches and methodologies. However, many existing studies exhibit certain limitations that must be taken into account. In [4], researchers developed an adaptive control system for Savonius rotor blades with automatic adjustment of the angle of attack to optimize performance in urban environments. Although the proposed method demonstrated improved overall system efficiency, the study did not consider critical nonlinear effects such as backlash and friction, which can negatively impact the positioning accuracy of aerodynamic elements under real operating conditions. In [5], researchers proposed an automatic control system for the aerodynamic flaps of a Savonius rotor to enhance energy efficiency. However, their analysis was limited to gradual changes in wind load, without examining the impact of sudden gusts and dynamic disturbances, which restricts the practical applicability of their solution under variable weather conditions. In [6], researchers investigated active control of aerodynamic elements in vertical-axis wind turbines to reduce mechanical stress and extend structural lifespan. However, their work lacked adaptive adjustment of control actions under dynamically changing wind conditions, which may reduce the system's overall stability and reliability. In [7], an adaptive PID control strategy was implemented, focusing on modifying regulator coefficients based on wind speed. While this research demonstrated favorable transient characteristics, it did not address issues related to mechanical clearances and impact loads, which can cause instability and wear of control components. In [8; 9], researchers focused on dynamic modeling and analysis of mechanical loads in vertical-axis wind turbines.