UAV collection methods for the farmland nodes data based on deep reinforcement learning

Unmanned Aerial Vehicle (UAV) has been widely used to collect data from the wireless sensor node in fields. Some problems can be solved in this case, such as no network infrastructure in farmland, fast power consumption of multi-hop data forwarding, premature death of nodes near the gateway, and shortened network life cycle. However, the multiple nodes overlapping can often occur during UAVs collection at the same time, due to the possible redundancy of adjacent sensor data. In this study, a UAV data collection method was proposed to plan the node selection, hovering position, and collecting order using improved deep reinforcement learning. The UAV data collection from the sensor nodes was then divided into two scenarios: data collection from the partial nodes under perceptual redundancy coverage, and data collection from all nodes. The optimization was made to save the UAV energy consumption in less mission completion time. The data collection of partial nodes under perceived redundancy coverage was suitable for the relatively high proportion of redundant coverage area among nodes. The UAV energy also failed to complete the data collection tasks of all nodes, indicating the low requirements of data integrity. By contrast, the all-node data collection fully met the high requirement of data integrity. In the scenario of partial node data collection with perceived redundant coverage, the Dueling Double Deep Q Network (DDDQN) was used to select the collection nodes and then plan the collecting order, indicating the high energy efficiency of the UAV with the less redundant data. Simulation results show that the DDDQN presented greater data coverage and lower effective coverage average energy consumption than the Deep Q Network (DQN) under the same configuration. The training process of DDDQN was more stable than that of DQN, particularly for the higher returns at the end of learning. More importantly, the flight distance and energy consumption of the DDDQN were reduced by 1.21 km, and 27.9%, respectively, compared with the DQN. In the scenario of all-node data collection, a Double Deep Reinforcement Learning (DDRL) was proposed to optimize the hovering position and UAV collection sequence, in order to minimize the total energy consumption of the UAV during data collection. A comparison was made on the DDRL with the classical PSO-TSP and MEFC. A systematic evaluation was made to clarify the impact of the UAV flight speed on the total energy consumption and total working time, the impact of different node data loads on the UAV energy consumption, the impact of different flight speeds on the UAV hover collection time, and the impact of the number of sensor nodes on the total energy consumption. The simulation results show that the total energy consumption of the improved model was at least 6.3% less than that of the classical PSO-based Travel Salesman Problem (PSO-TSP), and the Minimized Energy Flight Control (MEFC) under different node numbers and UAV flight speeds, especially at the data load of a single node less than 160 kB. Finally, the flight and hover powers of the quadrotor UAV were tested to determine the packet loss rate and received signal strength of the UAV in the field experiments. The actual field flight experiments were carried out on the DDRL and the data collection of the classical PSO-TSP. Field experiment results show that the DDRL-based data collection was reduced by 11.5% for the total energy consumption of UAV, compared with the PSO-TSP. The DDDQN and DDRL approaches can be expected to provide the optimal energy consumption for the UAVs' data collection of wireless sensor nodes in the field. © 2022 Chinese Society of Agricultural Engineering. All rights reserved.