Directional sensor placement in vegetable greenhouse for maximizing target coverage without occlusion

Wireless sensor network (WSN) is the key sensing resource for the internet of things (IoT) in vegetable greenhouse. The coverage control ensures that WSN can obtain enough effective information. However, the current coverage researches ignore the object size and lack of attention to the occlusion between targets. There are many leaves and fruits in vegetables, which can easily cause blind area and low utilization of directional sensors. Based on the geometric relationship between the directional sensors and targets, this paper studies a non-occlusion coverage scheme for the greenhouse IoT. Firstly, combined with the traditional coverage theory, a directional coverage model without occlusion is constructed by analysing the multivariate relationship between the sensor nodes and monitored targets. An objective function is then established to maximize the effective coverage. Based on the directional coverage model, this paper studies a hierarchical cooperative particle swarm optimization algorithm, which decomposes the global effective coverage problem into the utilization optimization of each sensor and finally get the orientation angle set. The experimental results show that the studied model and algorithm can avoid occlusion between covered objects while improving sensor utilization to a certain degree.