Monitoring and measuring Water quality of rivers, lakes, seas and oceans has been a critical question around the whole world. Traditionally, satellites are widely used for remote water sensing. Satellites can only give a larger view on water quality. They can't pin point a particular region, where we want to conduct a quality measurement. Due to the recent advancements in the fields of communication and sensing technology like Cyber Physical System (CPS) and wireless sensor network, efforts are on to build a wireless sensors deployed underwater for water quality surveillance. Sensors which are specifically developed for underwater environment, was able to collect critical water quality measurements like chemical substances,temperature etc. These sensors have advanced features like transmitting data through acoustic waves.
ZigBee is a specification for high level communication protocols which are based on the IEEE 802.15.4-2003 standard for Low Rate Wireless Personal Area Networks. These protocols use small, low power digital radios. Node distribution is optimized to reduce energy consumption and to ensure effective information acquisition in wireless sensor network. LR-WPANs are widely used for remote detection and real-time monitoring of natural water.
Proposed system will have a large number of sensor nodes which are placed in a lake. Sensors are implemented based on Zigbee wireless technology. A small no of UAVs will patrol the lake. UAVs are controlled by central monitoring station (CMS). wireless sensors can communicate directly with CMS or via other sensors. When data is collected from wireless sensors, the CMS is a sink and when guiding UAVs to pollution sources, it serves as both as a source and a sink because two way communication is needed for the control of UAVs. Sensors measurements will be send to signal processing circuit for local processing like quantization, scaling etc. After signal processing, signal is sent to microprocessor and finally to CMS system using TI-CC2430 transceiver circuit. Sensors use Li-ion battery as a power source. UAVs have its own sensors like acoustic sensor. UAVs have actuators like propeller,robot arms etc which are directly controlled by CMS.
Core component of CMS are
- Networked control algorithm
- Sensor selection algorithm
- Data fusion algorithm
Data fusion algorithm is used for water quality estimation based on the collected data, and find the exact location of pollution source. Sensor selection algorithm is used to choose a subset of sensors to activate at a given time. This is not an easy task, because batteries of wireless sensors has limited capacity and transmitting receiving message is the most energy consuming action.