Active Fault Tolerant Control of Livestock Stable Ventilation System

Mehdi Gholami

Research output: Book/ReportPh.D. thesis

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Abstract

Modern stables and greenhouses are equipped with different components for providing a
comfortable climate for animals and plant. A component malfunction may result in loss
of production. Therefore, it is desirable to design a control system, which is stable, and
is able to provide an acceptable degraded performance even in the faulty case.
In this thesis, we have designed such controllers for climate control systems for livestock
buildings in three steps:
Deriving a model for the climate control system of a pig-stable.
Designing a active fault diagnosis (AFD) algorithm for different kinds of fault.
Designing a fault tolerant control scheme for the climate control system.
In the first step, a conceptual multi-zone model for climate control of a live-stock
building is derived. The model is a nonlinear hybrid model. Hybrid systems contain
both discrete and continuous components. The parameters of the hybrid model are estimated
by a recursive estimation algorithm, the Extended Kalman Filter (EKF), using
experimental data which was provided by an equipped laboratory.
Two methods for active fault diagnosis are proposed. The AFD methods excite the
system by injecting a so-called excitation input. In both methods, the input is designed
off-line based on a sensitivity analysis in order to improve the precision of estimation of
parameters associated with faults. Two different algorithm, the EKF and a new adaptive
filter, are used to estimate the parameters of the system. The fault is detected and isolated
by comparing the nominal parameters with those estimated. The performance of AFD
methods depend on model accuracy, hence, the nonlinear model for the climate control
of the stable is used.
For the reconfiguration scheme, the nonlinear model is approximated to a piecewise
affine (PWA) model. The advantages of PWA modeling for controlling schemes are:
most complex industrial systems either show nonlinear behavior or contain both discrete
and continuous components which is called hybrid systems. PWA models are a relevant
modeling framework for such systems. Some industrial systems may also contain piecewise
affine (PWA) components such as dead-zones, saturation, etc or contain piecewise
nonlinear models which is the case for the climate control systems of the stables.
Fault tolerant controller (FTC) is based on a switching scheme between a set of predefined
passive fault tolerant controller (PFTC). In the FTC part of the thesis, first a
passive fault tolerant controller (PFTC) based on state feed-back is proposed for discretetime
PWA systems. only actuator faults are considered. By dissipativity theory and H1
analysis, the problem is cast as a set of linear matrix inequalities (LMIs). In the next contribution, the problem of reconfigurability of PWA systems is evaluated. A system
subject to a fault is considered as reconfigurable if it can be stabilized by a state feedback
controller and the optimal cost of the performance of the systems is admissible. In the
previous methods the input constraints are not included, while due to the physical limitation,
the input signal can not have any value. In continuing, a passive fault tolerant
controller (PFTC) based on state feedback is proposed to track a reference signal while
the control inputs are bounded.
Original languageEnglish
Number of pages179
ISBN (Print)123-223-445
Publication statusPublished - 2011

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