Focused Exploration for Cooperative Robotic Watercraft.

Abstract

Environmental monitoring is one of the main societal challenge of the last century. This is particularly important when considering the increasing population growth and the industrialization of developing countries. Information and Communication Technology (ICT) and robotics can play a significant role in this perspective as they offer invaluable tools to continuously gather relevant information over wide, possibly dangerous areas. In particular autonomous boats hold great promises for monitoring water bodies (lakes, rivers, fishfarms) or providing first aid in floods. However, a key feature for such systems to have a practical impact on society is to provide accurate measures over large areas while being cost effective. In this work, we focus on a water monitoring system, based on Cooperative Robotic Watercrafts (CRW), commercialised by Platypus LLC . The CRW approach is based on the use of low cost, small, robotics platforms, which are able to interact with each other and make use of various artificial intelligence methods to ensure a significant level of autonomy for navigation and information gathering tasks. Figure 1(a) shows a differential drive propeller versions. In addition to a battery based propulsion mechanism, each boat is equipped with an Android OS smartphone, custom electronics board, and sensor payload. The Android smartphone provides communication, GPS, compass, and multi-core processor. The Arduino Mega based electronics board receives commands from the Android phone and interfaces with the propulsion mechanism and sensor payload, as shown in Figure 1(b). The electronics board supports a wide variety of devices including acoustic doppler current profilers and sensors that measure temperature, Dissolved Oxygen (DO), and pH level. A crucial aspect for the CRW is the high level of autonomy of the platforms, which can be controlled by few human operators that provide high level instructions to the system. In particular, Figure 1(c) shows the Graphical User Interface that the human operators can use to control the robotic platforms. Boats behaviors are expressed in the form of high level plan encoded as Colored Petri Nets [1]. In this example, the human operator activated an explore area plan providing the shape of the area that must be explored. The platforms will then automatically divide the area in different sections and execute a pre-specified strategy to monitor the area. Figure 1(d) shows an example of the standard lawnmower strategy employed by the boats. Notice that such strategy is decided off-line, i.e., before the system acquires any readings, and as such it does not depend on the data that the platforms are collecting.