Physics-based Encapsulation in Embedded Software for Distributed Sensing and Control Applications

Feng Zhao, Chris Bailey-Kellogg, and Markus P.J. Fromherz

Abstract

Spatial Aggregation is an approach that abstracts data and computation on the data arising from distributed embedded sensing and control applications as a set of so-called "spatio-temporal objects". Locality and continuity in the underlying physics of the problem domain give rise to spatially coherent and temporally contiguous objects in an appropriate metric space. Once parameterized by physical properties such as location, intensity (e.g., light, temperature, pressure), and motion (e.g., velocity), these objects can be aggregated and abstracted into more abstract descriptions. Applications are written as the creation and transformation of these abstract objects.

We illustrate how these objects naturally arise from applications such as distributed sensing and actuation in an air-jet table system. Unlike in traditional software design, where objects and operations are defined mathematically and possess a semantics independent of possible implementations, the objects in distributed embedded software are defined by the physics of the application, algorithmic considerations, task requirements, as well as optimization criteria. The air-jet table example demonstrates that the grouping and abstraction of actuation devices are determined by laws of motion, the type of force allocation algorithms used, and the desired performance of the controller; this encapsulation greatly simplifies the design and implementation of a force allocation algorithm for the system and improves software modularity. Based on our practical experiences in designing several massively distributed sensing and actuation systems, we present a set of recommendations for distributed embedded software modeling and design.

For PDF file, send mail to fz@alum.mit.edu.

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