An overview of emerging results in networked multi-vehicle systems

Autonomous vehicle systems have been the topic of much research due to their ability to perform dangerous, repetitive and automated tasks in remote or hazardous environments. The potential for multi-vehicle systems cooperating together to accomplish given tasks is starting to draw together researchers from several fields, including robotics, control systems, and computer science. Multiple vehicles can be more effective than a single one, for example in information gathering tasks. By spreading out over the terrain to be searched, a cluster of autonomous helicopters, for example, can locate a target quite rapidly, or a group of coordinated autonomous underwater vehicles can search a coastal area for mines. In other cases, the coordinated operation of multiple vehicles can provide new capabilities. This is the case, for example, of the PATH strategy of platooning several vehicles as they travel along the highway, which may yield up to a four-fold increase in transportation capacity while enhancing safety. Another example is the Mobile Offshore Base, where semi-submersible modules are aligned to form a military base and runway at sea. The unprecedented length of the at-sea runway (up to a mile long) warrants the use of several modules. In each of these cases, there is a need for inter-vehicle communications so that each vehicle can know the status of the operation, the position of its counterparts, and whether the specific mission goals have changed. Thus the control and communication problems become inexorably tied. However, few results are available to analyze performance and stability of a closed loop system where some of the loops are closed by communicated variables. Using the above examples as a motivation, this paper examines emerging results in networked multi-vehicle systems. Recent work has taken many different approaches, such as hybrid systems, distributed control, differential games, control architectures, and artificial intelligence. The focus of this paper is on the control systems perspective. We attempt to present some current issues common to networked multi-vehicle systems, and to show how they have been solved to date in the perspective of the case studies.