Computer-Aided Design of a Generic Robot Controller Handling Reactivity and Real-Time Control Issues

This paper describes an original system, Open Robot Controller Computer-Aided Design (ORCCAD), for the computer-aided design of robot controllers. Accessed by three different user levels (system, control, and application), it proposes 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 through the literature, the paper presents the basic principles and underlying concepts of ORCCAD. 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 full definition of which requires the specification of temporal and synchronization features. 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. The first one consists in the specification and the test of a few versions of a joint control for a rigid robot; the other one is a mission specification for an autonomous underwater vehicle. Dialogue and verification tools are integrated within ORCCAD: a graphical human-machine interface used to build the robot tasks and a simulation software dedicated to hybrid continuous/discrete time simulations.