We therefore designed a connecting circuit between the corrosion-detecting device and the MicaZ mote, and the circuit functions by transforming the current output of the corrosion events into a voltage that can be measured by the MicaZ. We have to map each voltage reading of ADC channel of MicaZ into a current reading. Figure 2 shows the kernel part of the circuit [28]. The accuracies of the potential and current measurements are 10?5 V and 10?7 A, respectively.Figure 2.Sc
A usual dichotomy partitions robot visual navigation methods into quantitative and qualitative methods [1]. The estimation of metric position information is not needed in a qualitative method, and the environments are usually represented by a route. It is crucial for robots to move autonomously from their current position to the home position along the route.
Numerous methods for route guidance have been proposed, including node-based [2�C6] ones and those that do not use nodes [7,8]. Navigation models that do not separate routes into sequences of waypoints have been proposed in [7,8], following the widely neglected branch of models based on recognition-triggered response. The navigation with nodes has been modeled by local visual homing strategies [2�C5]. Inspired by the simple principle of biological navigation, local visual homing has the ability to return to a previously visited location, and has drawn attention in robotics study as computationally cheap building blocks in a minimalistic appearance-based navigation framework.
In this paper, we present that long-range homing along a route can be achieved by implementing local visual homing strategy to sequentially visit the topological nodes. In the feature-based local visual homing in unprepared environments, the extracted visual features are ideal alternatives to artificial landmarks. However, a big challenge during long-range homing in changing environments is the management of rich feature sources [9,10]. In order to avoid irrelevant and redundant features, task-oriented selection schemes are needed, which contain additional constraints in evaluating feature usefulness for the tasks. Furthermore, in order to obtain optimal features during long-range navigation, it is necessary to maintain an up to date representation of surrounding environments.
Propelled by above requirements, the main work of this paper focuses on the feature optimization orienting towards long-range feature-based visual homing GSK-3 in changing environments.Several feature-based visual homing strategies have been presented in the literature, such as average displacement vector [11], average landmark vector (ALV) [12] and the included angle difference method [2]. However, they all need or imply an equal-distance assumption that all landmarks are distributed at the same distance from the snapshot location.