This paper addresses the problem of thrust estimation and control for the rotors of small-sized multirotors Uncrewed Aerial Vehicles (UAVs). Accurate control of the thrust generated by each rotor during flight is one of the main challenges for robust control of quadrotors. The most common approach is to approximate the mapping of rotor speed to thrust with a simple quadratic model. This model is known to fail under non-hovering flight conditions, introducing errors into the control pipeline. One of the approaches to modeling the aerodynamics around the propellers is the Blade Element Momentum Theory (BEMT). Here, we propose a novel BEMT-based closed-loop thrust estimator and control to eliminate the laborious calibration step of finding several aerodynamic coefficients. We aim to reuse known values as a baseline and fit the thrust estimate to values closest to the real ones with a simple test bench experiment, resulting in a single scaling value. A feedforward PID thrust control was implemented for each rotor, and the methods were validated by outdoor experiments with two multirotor UAV platforms: 250mm and 500mm. A statistical analysis of the results showed that the thrust estimation and control provided better robustness under aerodynamically varying flight conditions compared to the quadratic model.

翻译：本文针对小型多旋翼无人飞行器（UAV）旋翼的推力估计与控制问题展开研究。在飞行过程中精确控制每个旋翼产生的推力是实现四旋翼飞行器鲁棒控制的主要挑战之一。最常见的方法是通过简单的二次模型近似描述旋翼转速与推力的映射关系。已知该模型在非悬停飞行条件下会失效，从而在控制流程中引入误差。桨叶叶素动量理论（BEMT）是建模螺旋桨周围空气动力学的方法之一。本文提出一种基于BEMT的新型闭环推力估计与控制方法，以消除寻找多个空气动力学系数所需的繁琐校准步骤。该方法以已知参数为基准，通过简易实验台架实验将推力估计值拟合至最接近真实值的状态，最终仅需获取单一比例系数。我们为每个旋翼实现了前馈PID推力控制，并通过250mm与500mm两种多旋翼无人机平台的户外实验验证了所提方法。结果统计分析表明，与二次模型相比，该推力估计与控制方法在空气动力学条件变化的飞行环境中具有更好的鲁棒性。