An autonomous robot offers a challenging and ideal field for the study of intelligent architectures. Autonomy within a rational be havior could be evaluated by the robot's effectiveness and robust ness in carrying out tasks in different and ill-known environments. It raises major requirements on the control architecture. Further more, a robot as a programmable machine brings up other archi tectural needs, such as the ease and quality of its specification and programming.This article describes an integrated architecture that allows a mobile robot to plan its tasks—taking into account temporal and domain constraints, to perform corresponding actions and to con trol their execution in real-time—while being reactive to possible events. The general architecture is composed of three levels: a de cision level, an execution level, and a functional level. The latter is composed of modules that embed the functions achieving sensor- data processing and effector control. The decision level is goal and event driven, a...

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An Architecture for Autonomy

The manufacturing environment has changed dramatically. In the past, manufacturing systems were sufficiently simple, in most cases, to permit the use of intuitive and informal solutions in the development of supervisory control systems. The increasing level of automation, integration, and flexibility encountered in automated manufacturing systems renders formal approaches to the supervisory control system development a necessity, The controlled-automata based approach to supervisory control development considered in this work is one such approach. It offers important advantages over other approaches. It guarantees that: i) the resulting controlled behaviors do not contradict the behavioral specifications and are nonblocking and ii) the controlled behaviors are maximally permissive within the behavioral specifications. The work presented illustrates the applicability of the method to the supervisory control of industrial automated manufacturing systems. The paper provides an overview of the automated manufacturing field, and introduces supervisory-control-system development. The main concepts are illustrated through an example of a small manufacturing cell. The development of a supervisory control system for an experimental manufacturing cell is presented subsequently. Both centralized and modular supervision are considered. The automata models for the complete cell are provided together with the corresponding supervisors. The implementation of the resulting supervisory control system only required the use of "off-the-shelf" industrial control systems.

The real-time supervisory control of an experimental manufacturing cell

An original system, Open Robot Controller Computer-Aided Design (ORCCAD), for the computer-aided design of robot controllers is described. Accessed by three different user levels (system, control, and application), it provides a coherent approach from a high-level specification down to its implementation, and offers several tools for design, display, and test. Following a critical study of the main architectures reported in the literature, the basic principles and underlying concepts of ORCCAD are presented. The main entity considered is the robot task, an elementary control action associated with a local behavior controlled by a set of observers and modeled by a finite-state automaton. It is made of a set of real-time communicating tasks, called module tasks. The module task which handles the behavior of the robot task, is described using the synchronous language ESTEREL. The application level is defined as a set of synchronized robot tasks, also described using ESTEREL. Two detailed examples are discussed. >

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Computer-aided design of a generic robot controller handling reactivity and real-time control issues

An open architecture manufacturing system pursues to integrate manufacturing components on a single platform. Therefore, a particular component can be easily added and/or replaced. In this paper, a modular and object-oriented approach for the PC-based open robot control (PC-ORC) system is investigated. A standard reference model for controlling robots, which consists of a hardware platform, an operating system module, and various application software modules, is first proposed. Then, PC-ORC system, which can reconfigure the control system in various production environments, is developed. The PC-ORC is constructed based upon the object-oriented method. Hence, it allows an easy implementation and modification of various modules. The PC-ORC consists of basic software, application objects, and additional hardware devices on a PC platform. Finally, by applying the proposed PC-ORC to a SCARA robot, the performance of the PC-ORC is examined.

A PC-based open robot control system: PC-ORC

This paper proposes a formalism for the description and automated implementation of the functional modules of an autonomous mobile robot in the framework of multi-layered control architectures. The formalization of the description of a module, including its behavior and its interfaces with other modules makes the implementation easier by providing higher level tools and automatic consistence checking tools in the module compiler. The execution control level can take advantage of the formal description of the activity tree of the modules to manage the resources more efficiently. A global task of the robot is achieved by the control system by connecting the modules into a dynamic activity tree. Finally the authors present a modules compiler that uses the formal module description and user supplied functions to produce the modules in an automated way. >

Design of a modular architecture for autonomous robot

The authors present some design issues for a task-level controller based on a specific control approach. The achievement of a robotic application requires the use of a large set of cooperating devices such as manipulators and sensors. An application is performed by scheduling several actions of the system. Each action is modeled with a functional aspect (control law) and a behavioral one (reactions on events). These two aspects are combined in a single object, the robot-task. An object-oriented approach was used to model these actions. The synchronous language Esterel was used both to program an application at the end-user level and to program the behavioral part of the robot-tasks at the control level. The main design issues of a real-time controller able to implement and perform these actions are outlined. >

E. CosteManiere

Papers

Reactive objects in a task level open controller