A Deep Reinforcement Learning-Based Adaptive Control Strategy for UAVs in Dynamic and Complex Environments

The increasing usage of Unmanned Aerial Vehicles (UAVs) in diverse applications necessitates the development of effective flight control systems. A major difficulty, nevertheless, is maintaining robust flight control under complex and dynamic environmental conditions, such as obstacle and non-flying zones, wind disturbances, and sensor noise. Traditional control techniques fail to achieve required flight control in these environments. To address this point, an adaptive control strategy is proposed based on a Deep Reinforcement Learning (DRL) model to enhance the flight performance of quadcopters. The learning and adaptation of the DRL-based control strategy are implemented in real-time through continuous interaction with the environment. This is to improve flight control and achieve consistent UAV performance under varying conditions. Proximal policy optimization with a reward function is used to minimize positional errors, ensure collision-free flight paths, and reduce energy consumption. The developed DRL model for quadcopters is trained in a simulated environment and then tested in three complex environmental scenarios, including urban, forest and mountain terrains. Experimental results demonstrate remarkable improvements in UAV flight performance. In the training phase, the reported training reward increased from 10 to 110 and the train loss is dropped from 0.85 to 0.05, which indicated successful model learning. Also, during system verification, rewards increased from 12 to 115 and UAV flight path deviations were decreased from 0.5 to 0.08m. The proposed controller outperforms conventional approaches in urban environments by lowering average trajectory deviations to 0.2m from 0.35m for MPC and 0.6m for PID. Also, the developed DRL-based controller outperformed the PID and MPC controllers, with path deviations of 0.18m in mountains and 0.12m in forests. In addition, fewer collision rates with obstacles are achieved with the model, 3% in forest, 1.8% in urban areas, and 4.5% in mountains. Furthermore, the consumed energy is reduced to 950J as compared to 1200J for PID and 1050J for MPC. The results show the strength of deploying the proposed controller in following the intended UAV flight path with high precision, effectively avoiding detected conflicts and minimizing consumed energy by the UAV.