Chapter 9 Coordination in Sensor , Actuator and Robot Networks

This chapter surveys the existing representative work in both sensor-actuator and actuator-actuator coordination. Sensor-actuator coordination deals with establishing data paths between sensors and actuators, and can be used for sensor deployment. Actuatoractuator coordination includes robot coordination for sensor placement, dynamic task allocation, selecting best robot to respond to reported event, robot dispersion, boundary coverage, and fault tolerant response. In coordinated actuator movement problem, actuators are moved to desired locations to save energy in long-term communication tasks where the traffic is sufficiently regular and large in volume to warrant nodes expending energy for moving. A recent study on coordination among flying robots is introduced in the end. 9.1. Sensor-actuator coordination The collaborative operation of sensors enables the distributed sensing of a physical phenomenon. In WSNs (wireless sensor networks), the sink (base station) performs the functions of data collection, processing and coordination. In WSANs (wireless sensor and actuator networks), both sensor-actuator and actuator-actuator coordination are required. After sensors detect an event that has occurred in the environment, the event data is processed (e.g. aggregated with reports from nearby sensors) and transmitted to the actuators, which gather, process, and eventually reconstruct the characteristics of the event. The process of establishing data paths between sensors and actuators is referred to as sensor-actuator coordination [MPGA07]. Sensor-actuator coordination provides the transmission of event features from sensors to actuators. Sensors and actuators coordinate also for some other tasks, such as sensor placement or improving connectivity. Akyildiz and Kasimoglu [AK04] did the first comprehensive analysis on both sensoractuator and sensor-sensor coordination. There are few main requirements on the communications in sensor-actuator coordination [AK04]. The communications between sensors and actuators in WSANs require energy efficiency to prolong the lifetime of the network. In some real-time applications, e.g., detection of fire, the communication traffic is typically delay sensitive. Therefore, sensor-actuator communication should support real-time traffic in these applications. The sensor-actuator communication is also required to ensure ordering of event data reported to the actuators. For example, suppose there are two sensors reporting two different events to a common actuator. These two events may