Actor-Oriented Control System Design
Jie Liu, Johan Eker, Xiaojun Liu, John Reekie, and Edward A. Lee
IEEE Transactions on Control System Technology, special issue on Computer Automated Multi-Paradigm Modeling, March, 2002.
ABSTRACT
Complex control systems are heterogeneous, in the sense of discrete computer-based controllers
interacting with continuous physical plants, regular data sampling interleaving with usually irregular
communication and user interaction, and multilayer and multimode control laws. This heterogeneity
imposes great challenges for control system design technologies in terms of end-to-end control performance
modeling and simulation, traceable refinements from algorithms to software/hardware implementation,
and component reuse. This paper presents an actor-oriented design methodology that tames these
issues by separating the data-centric computational components (a.k.a. actors) and the control-flow-centric
scheduling and activation mechanisms (a.k.a. frameworks). The underlying principle of frameworks is to use formal models of computation to manage the interactions among actors. Semantically different frameworks
can be composed hierarchically to manage heterogeneity, improve understandability, and achieve
actor and framework reusability. This methodology is implemented through the Ptolemy II software environment.
As an example, the methodology and the Ptolemy II software have been applied to the design of
a pendulum inversion and stabilization system.