Energy-efficient automatic monitoring system of aquaculture based on WSN

Abstract: Because of the expanding scale of aquaculture and rising labor costs, it is urgent to establish an automatic monitoring and control system of water quality. The optimized protocol of centralized low-power hierarchical clustering (LEACH-C) for a wireless sensor network communication and frequency control aeration system based on a programmable logic controller (PLC) was adopted. In a LEACH-C communication protocol, cluster heads were selected according to the residual energy of each node by the base station with fixed power supply. The aim of balancing the residual energy of each node was reached. From the actual control accuracy of the system, the changes in dissolved oxygen concentration was less than 0.02 mg/L than the value last time, and the corresponding node sent no data to its cluster head for saving energy. The test proved that the lifetime of a network adopted optimized LEACH-C protocol was 33.33% longer than that of a network adopted conventional LEACH protocol. The concentration of dissolved oxygen in water which was suitable for the perch growth was no less than 4.5 mg/L. As the concentration increased, the aeration efficiency will be gradually reduced. Therefore, the range of emergency oxygen was set from 4.5 to 5.5 mg/L. Based on measured value of dissolved oxygen content from the wireless sensor networks, a PI-PID algorithm was used in controlling the concentration of dissolved oxygen in the water body. When the error was large, the use of a set of PI parameters could quickly narrow the error; while error-hour, using a set of PID parameters could remain stable. In order to ensure the smooth switching of the two sets of parameters, a hysteresis switching area was set. This would ensure the timeliness and efficiency in oxygen supply when the dissolved oxygen concentration in water was less than 4.5 mg/L, or more than 5.5 mg/L. The dissolved oxygen in water was always suitable for the growth of fish. It is verified by experiment that compared with the artificial rough control, labor costs were significantly reduced and nearly half of the electricity was saved by this control method.