This paper deals with the architecture and control structure of mobile robots. The authors decompose robot functions into modules organized according to their predefined interactions: sensor modules that accomplish various processings on data from physical sensors, effector modules that issue commands to effectors, servo-processes that establish links between perception and action to achieve closed-loop behaviors, and functional units that provide specific functionalities. These modules, and hence the robot system itself, are controlled by a control system that also enables the robot to execute missions (plans) expressed in a command language. The authors introduce and discuss a generic control system structure, composed of a supervisor that interprets the plan and oversees its execution, an executive for operating and managing robot modules and resources, a surveillance manager for detecting and reacting to asynchronous events, and an error recovery module for local plan mending and correction. Several experimental examples are given.>

The author describes an architecture for cooperative and autonomous mobile robots. The cooperation is composed of two phases: collaboration where a task is decomposed into subtasks and subtasks are allocated through a set of robots, and coordination where robots actually coordinate their activities to fulfil the initial task using the notion of coordinated protocols. This architecture exhibits benefits such as (1) modularity (the robot can work autonomously or within a team); (2) robustness (although some modules on the robot fail, it is still able to perform useful tasks); and (3) programmability. An example using two real robots is described to show the approach.>

This paper presents an architecture supporting cooperation for multiple mobile robots that is jlezible enough to support different forms of control (local, distributed, and centralized). We argue that it is possible to envision cooperation between robots for simple battlefield strategies (tandem, movement in formation, and convoying) using this. architecture. The cooperation involves few vehicles and is based on a distributed control organization. Several ezamples are discussed and one of them has been fully implemented on two indoor mobile robots. Finally, extensions such as man-machine interface and a mission-assistance system are presented.

It is pointed out that the purpose of an autonomous mobile robot is to achieve various tasks while adapting its behavior to the variations of its environment. Therefore, such a robot needs both reflexive and planning capabilities. It appears that combining these is difficult; indeed, some robot architectures exhibit a high degree of reactivity, but poor planning abilities, or vice versa. The authors attempt to show that the integration of reflexive and planning capabilities is feasible. A novel generic architecture, composed of three levels, functional, control, and planner, is proposed. It provides important features such as progressive and programmable reactivity, robustness, and versatility. All these features are described at each level. A complete implementation in an experimental mobile robot is described, and an actual example is presented.>

Describes an algorithm for collision avoidance between multiple mobile robots. As robots actually exchange information, algorithms are based on two hypotheses: (i) the working space is decomposed into cells and a limited number of robots is affected to each cell-thus a robot exchanges information only with robots in its vicinity and (ii) the trajectory of a robot is decomposed into sections-thus robots exchange only relevant information among themselves. A pipeline algorithm is proposed where a robot computes collisions with other robots on the section S/sub j+1/ while the it moves along the section S/sub j/. These algorithms are fully integrated in a more general architecture for mobile robots. Examples are described to show the interest of this approach.>

This paper describes a man/machine interface and its integration into a more general architecture for incompletely autonomous mobile robots. The architecture is composed of four levels, the functional level, the control level, the planner level, and the man/machine level. This architecture provides reactivity, execution monitoring and planning. Arguments are given to motivate the need for a man/machine interface for a mobile robot. With this interface, the operator has access to all of the levels of the architecture and this increases the robustness of the overall architecture. Some examples are given.>

An approach to handling error recovery for mobile robots is proposed. To understand the way in which detection, error analysis, and mission insertion are carried out, the decomposition of missions into statements is introduced, followed by the notion of a token. The goal of tokens is to manipulate statements. Error recovery is based on the development of a failure tree using an error knowledge base. Moreover, the architecture includes detection of hardware malfunctions at different levels. It is shown through examples that the token structure gives a good representation of mission execution and that error recovery enhances the flexibility and reliability of the overall architecture.>