Ensuring Reliability and Fault-Tolerance for the Cyber-Physical System Design

Name: Volkan Gunes
Date: May 27, 2015

Time: 11:00AM – 12:00PM

Location: Donald Bren Hall 3013 Conference Room

Committee: Tony Givargis (Chair), Alexandru Nicolau, Ian Harris, Steffen Peter

Abstract:

The cyber-physical system (CPS) is a term describing a broad range of
complex, multi-disciplinary, physically-aware next generation engineered
systems that integrate embedded computing technologies (cyber part) into
the physical world. Sensors play an important role in this integration
because they provide the data extracted from the physical world for the
cyber systems to fulfill the decision making process. However, this
process is likely to be misled by incorrect data due to sensor fault
occurrences.

In this dissertation, the main focus is on sensor fault mitigation and
achieving high reliability in CPS operations. One of the challenges we
ponder is timely event (e.g., motion as a phenomenon) detection in CPS
under possible faulty sensor conditions. In this regard, our
demonstrative example of CPS is the falling ball example (FBE) using
binary event detectors (i.e., motion sensors), a controller, and a
camera for timely motion detection of a falling ball. Another challenge
we ponder is satisfying thermal comfort and energy efficiency under
certain faulty sensor conditions in a multi-room building incorporating
temperature sensors, controllers, and heating, ventilation, and air
conditioning (HVAC) systems as a CPS application. For both cases, we
adopt a model-based design (MBD) methodology to analyze the effect of
sensor faults on the desired system outcome. We specify well-defined
fault semantics for the event detectors and temperature sensors to make
the problem definition more clear. We provide a MATLAB/Simulink
simulation framework for our CPS examples. Besides having the
traditional CPS model that comprises the cyber, interface (e.g. sensors
and actuators) and physical models, we develop fault models and a system
evaluation model in Simulink and incorporate them into the CPS model.

We explore various techniques for fault mitigation in a holistic design
perspective. Therefore, the approaches presented in this study
contributes to the design of fault-tolerant CPSs. Furthermore,
considering compute demands of large scale CPSs, we introduce the XGRID
embedded many-core system-on-chip architecture. XGRID makes use of a
novel, FPGA-like, programmable interconnect infrastructure, offering
scalability and deterministic communication using hardware supported
message passing among cores. We provide a conceptual mapping of control
algorithms for the automation of a multi-room building onto target XGRID
architecture.

Our findings regarding reliable CPS design show that the physical system
attributes (e.g., sensor placement and environmental effects) can be a
more dominant factor than the cyber system attributes on the system
outcome. In addition, sensor faults may lead to unsatisfactory system
outcome in CPSs since CPSs heavily rely on sensor readings for decision
making. Therefore, the analysis of temporal and spatial correlations
between sensor readings helps mitigate certain types of sensor faults
and enable CPSs to utilize sensors’ data more efficiently for decision
making.