Seminar Details
2011-12-06 (14.00) : Modeling, analysis and design of multi-hop control networks
At Euler building
Organized by Mathematical Engineering
Speaker :
Alessandro D'Innocenzo (University of L'Aquila)
Abstract :
A multi-hop Control Network (MCN) consists of a plant where the
communication between sensors, actuators and computational units is
supported by a (wireless) multi-hop communication network, and data
flow is performed using scheduling and routing of sensing and
actuation data. We propose a mathematical framework for modeling and
analyzing systems consisting of multiple control loops closed over a
multi-hop (wireless) communication network. We separate control,
topology, routing, and scheduling and propose formal syntax and
semantics for the dynamics of the composed system, providing an
explicit translation of multi-hop control networks to switched
systems. We propose formal models for analyzing robustness of
multi-hop control networks, where data is exchanged through a
multi-hop communication network subject to disruptions. When
communication disruptions are long, compared to the speed of the
control system, we propose to model them as permanent link
failures. We show that the complexity of analyzing such failures is
NP-hard, and discuss a way to overcome this limitation for practical
cases using compositional analysis. For typical packet transmission
errors, we propose a transient error model where links fail for one
time slot independently of the past and of other links. We provide
sufficient conditions for almost sure stability in presence of
transient link failures, and give efficient decision procedures. We
deal with errors that have random time span and show that, under some
conditions, the permanent failure model can be used as a reliable
abstraction. Our approach is compositional, namely it addresses the
problem of designing scalable scheduling and routing policies for
multiple control loops closed on the same multi-hop control
network. We describe how the translation of multi-hop control networks
to switched systems can be automated, and use it to solve control and
networking co-design challenges in some representative examples, and
to propose a scheduling solution in a mineral floatation control
problem that can be implemented on a time triggered communication
protocols for wireless networks. We address the control design problem
on a MCN that is subject to link failures, where the plant is a SISO
LTI system. We first characterize controllability and observability of
a MCN, by means of necessary and sufficient conditions on the plant
dynamics and on the communication scheduling and routing. We provide a
methodology to design scheduling and routing, in order to satisfy
controllability and observability of a MCN for any link failure that
preserves connectivity of the radio connectivity graph. Then, we
characterize the problem of detecting the failure of links of the
radio connectivity graph: we provide necessary and sufficient
conditions on the plant dynamics and on the communication protocol,
and we provide a methodology to design the network topology,
scheduling and routing to satisfy the above conditions.