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Cyber-Physical System Requirements - A Model Driven Approach
Background
Cyber-physical systems (CPS) – networked
software based systems that extensively
interact with the physical world. Eg: Aircraft
control devices
FDA’s initiative explores various methods to
improve the safety of medical CPS systems
such as infusion pumps.
Complete and consistent requirements are
central to analysis, verification, and assurance
for safety.
Collecting a good set of requirements is not a
straightforward task.
A generic patient controlled analgesia (GPCA)
infusion pump system was used as a case
example to provide an archetype of system
development artifacts that demonstrates safety.
Publications
1. A.Murugesan, S.Rayadurgam, M.Heimdahl. Using Models to
Address Challenges in Specifying Requirements for Medical
Cyber-Physical Systems. Accepted at Fourth workshop on
Medical Cyber-Physical Systems, Philadelphia, PA, Apr
2013.
2. Mats.Heimdahl, L.Duan, A.Murugesan, S.Rayadurgam.
Modeling and Requirements on the Physical Side of Cyber-
Physical Systems. Accepted at Second International
Workshop on the Twin Peaks of Requirements and
Architecture, San Francisco, CA, May 2013.
3. A.Murugesan, S.Rayadurgam, M.Heimdahl. Modes, Features,
and State-Based Modeling for Clarity and Flexibility.
Accepted at Fifth International Workshop on Modeling in
Software Engineering , San Francisco, CA, May 2013.
Research Challenges
Requirements Analyses and Modeling Techniques
Abstract
Gathering and analyzing Cyber-Physical System
requirements pose unique challenges to the
requirements engineering community - a
perspective that is sensitive to the scoping and
interplay between the cyber, physical and
behavioral aspects of the system. A model driven
requirements analysis approach using various
categories of models served as a useful aid in
discovering, understanding, and analyzing certain
classes of requirements about crucial aspects of
the cyber-physical systems which were otherwise
latent.
©2008 Regents of the University of Minnesota. All rights reserved.
Anitha Murugesan, Lian Duan, Sanjai Rayadurgam, Mats Heimdahl Department of Computer Science and Engineering, University of Minnesota-Twin Cities
Next Steps
Create assurance cases and perform reasoning to demonstrate GPCA safety
Create a catalog of requirements patterns to capture system dynamics in the
physical domain. (Control System Modeling)
Develop guidelines for scoping a system and flow-down of requirements to
decomposed system components. (Architectural Modeling)
Build a catalog of solutions for various behavioral modeling problems and
build a repertoire of modeling patterns. (Stateflow Modeling)
Develop a standard set of reference artifacts for demonstrating the safety of
CPS systems.
Requirements to address the complexity in the continuous domain.
Requirements categories related to continual behavior of the system
Precise scoping of the system.
Understanding requirements and system decomposition.
Understanding modes and features interactions
Analyzing system behavior during mode transitions.
Modeling for change/expansion/contraction.
Control System Modeling Architectural Modeling
• Examine different architectures.
• Visualize hierarchical system decomposition
• Precisely fixed system boundary to express
requirements.
Stateflow Modeling
• Evaluate various control strategies
• Explore system responses in its
intended environment.
• Identified categories of requirements:
• Accuracy
• Rise / Drop Time
• Rate of Change
• Overshoot (Max deviation)
• Settling Time
• Cumulative Error
• Complement requirements to
understand the dynamic behavior of
complex systems.
• Analyze mode-logic requirements
and behavior.
• Identified mode-logic modeling
patterns that are flexible for
changes.
• Sequential vs Parallel structure of
mode logic
• Complex feature behaviors
Figure: Generic Patient Controlled Analgesia Infusion Pump System.
Figure: Infusion Pump Plant Model.
Figure: Infusion System – GPCA Device Architecture Model
Figure: GPCA Software Model Overview
Figure: GPCA Software Model – Infusion Manager Subsystem
Funded by CNS-0931931
and CNS-1035715