Technical Reports

The ICICS/CS Reading Room

UBC CS TR-94-26 Summary

A Foundation for the Design and Analysis of Robotic Systems and Behaviors, October 1994 Zhang Ying, 245 pages

Robots are generally composed of electromechanical parts with multiple sensors and actuators. The overall behavior of a robot emerges from coordination among its various parts and interaction with its environment. Developing intelligent, reliable, robust and safe robots, or real-time embedded systems, has become a focus of interest in recent years. In this thesis, we establish a foundation for modeling, specifying and verifying discrete/continuous hybrid systems and take an integrated approach to the design and analysis of robotic systems and behaviors.

A robotic system in general is a hybrid dynamic system, consisting of continuous, discrete and event-driven components. We develop a semantic model for dynamic systems, that we call Constraint Nets (CN). CN introduces an abstraction and a unitary framework to model discrete/continuous hybrid systems. CN provides aggregation operators to model a complex system hierarchically. CN supports multiple levels of abstraction, based on abstract algebra and topology, to model and analyze a system at different levels of detail. CN, because of its rigorous foundation, can be used to define programming semantics of real-time languages for control systems.

While modeling focuses on the underlying structure of a system --- the organization and coordination of its components --- requirements specification imposes global constraints on a system's behavior, and behavior verification ensures the correctness of the behavior with respect to its requirements specification. We develop a timed linear temporal logic and timed $\forall$-automata to specify timed as well as sequential behaviors. We develop a formal verification method for timed $\forall$-automata specification, by combining a generalized model checking technique for automata with a generalized stability analysis method for dynamic systems.

A good design methodology can simplify the verification of a robotic system. We develop a systematic approach to control synthesis from requirements specification, by exploring a relation between constraint satisfaction and dynamic systems using constraint methods. With this approach, control synthesis and behavior verification are coupled through requirements specification.

To model, synthesize, simulate, and understand various robotic systems we have studied in this research, we develop a visual programming and simulation environment that we call ALERT: A Laboratory for Embedded Real-Time systems.

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