Page 44 - ASME DSCC 2015 Program

Technical Program

Numeric and analytic Investigations of Mean-Square exponential InVITED SESSIon
Stability for Stochastically Timed Systems 2-5-1 TA4 HVAC Building Energy Management
Contributed short paper. DSCC2015-9810 Geroge Bellows f 10:00am–12:00pm
Dylan Poulsen, Washington College, Chestertown, MD, United States,
Ian Gravagne, John Davis, Baylor University, Waco, TX, United States Session Organizer: Bryan Rasmussen, Texas A&M University
Session Organizer: Vahid Dehkordi, Natural Resources, Canada
This paper is motivated by the problems posed in feedback control design
Session Chair: Christopher Price, Texas A&M University
when actuators, sensors, and/or computational nodes connect via unreli-
Session Co-Chair: Donald J. Docimo, The Pennsylvania State University
able or unpredictable communications channels. In these cases, there is a
degree of stochastic uncertainty to the timing of the system’s discretizing
characterization of damping and Beating effects Within the aggregate
elements, such as digital-to-analog converters. Several theorems related
Power Demand of Heterogeneous Thermostatically Controlled loads
to the stability of non-uniformly sampled discrete dynamical systems have
Invited session paper. DSCC2015-9803
recently been proposed; here we examine through numeric investigation
Donald J. Docimo, Hosam K. fathy, The Pennsylvania State University,
the characteristics of systems which are mean square exponentially stable
University Park, PA, United States
(MSES). In particular we present a method to compute the range of mean
and variance that a nonuniformly discretized feedback control system may This paper presents an analysis of the damping and beating effects within
tolerate while remaining MSES. Several examples are presented. the aggregate power demand of heterogeneous thermostatically controlled
loads (TCLs). Demand response using TCLs is an appealing method to
Experimental Investigation of a Time Scales-Based Stability Criterion
enable higher levels of penetration of intermittent renewable resources into
over finite Time Horizons
the electric grid. Previous literature covers the benefits of TCL population
Contributed short paper. DSCC2015-9887
heterogeneity for control purposes, but the focus is solely on the damping
Matthew Mosley, Ian Gravagne, John Davis, Baylor University, Waco, observed in these systems. This work is, to the best of the authors’ knowl-
TX, United States, Dylan Poulsen, Washington College, Chestertown, MD, edge, the first to characterize the combined damping and beating response
United States
of power demand versus the level of TCL population parameter hetero-
Feedback control systems that employ large area networks or other unpre- geneity. The forced aggregate dynamics of TCLs have been shown to be
dictable or unreliable communications protocols between sensors, actua- bilinear when set point temperature adjustment is used as a control input.
tors, and controllers may experience nonuniform sampling characteristics. This motivates the paper’s use of free response dynamics, which are linear,
Previous work by Poulsen, et. al. gives a criterion for exponential stability of to characterize both the damping and beating phenomena. A stochastic
non-uniformly discretized feedback control systems, assuming sample peri- parameter distribution is applied to the homogeneous power demand solu-
ods drawn from a known statistical distribution. However, the given stability tion, furnishing an analytic expression for aggregate power demand. The
theorem assumes an infinite time horizon. This work therefore examines the resulting analysis shows that increasing parameter heterogeneity increases
exponential stability criterion experimentally, over a finite time horizon, on a damping and shortens the beat period.
2nd-order servo mechanism.
effective Tuning of cascaded control Loops for Nonlinear hVac
decoupling Transformations for Linear Systems in the configuration Systems
Space Invited session paper. DSCC2015-9806
Contributed regular paper. DSCC2015-9746
Christopher Price, Bryan Rasmussen, Texas A&M University, College
Cornel Sultan, Virginia Tech, Blacksburg, VA, United States Station, TX, United States
Recent major breakthroughs have been achieved in providing transforma- Residential and commercial buildings are large consumers of energy in the
tions that completely decouple all second order linear time invariant systems United States with Heating, Ventilation, and Air-Conditioning systems repre-
directly in the configuration space. A brief review is presented herein. senting a significant portion of total use. These systems control aspects such
as humidity and room air temperature to ensure building occupant comfort.
Control of HVAC units presents unique challenges due to large nonlineari-
ties heavily dependent on operating conditions. Static linear controllers are
unable to counteract such nonlinearities resulting in sustained oscillations
known as hunting behavior. Previous research has shown the ability of
cascaded architectures to compensate for HVAC nonlinearities and improve
overall system performance without the need for detailed dynamic models.
To aid the implementation of cascaded loops on real building systems,
analysis of the effects of inner loop gain are presented and three outer loop
tuning cases are identified. A simulation case study of an Air Handling Unit
demonstrates the simplicity of the procedure and compares it with optimally
tuned gains.

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