1,139 research outputs found
Flat systems, equivalence and trajectory generation
Flat systems, an important subclass of nonlinear control systems introduced
via differential-algebraic methods, are defined in a differential
geometric framework. We utilize the infinite dimensional geometry developed
by Vinogradov and coworkers: a control system is a diffiety, or more
precisely, an ordinary diffiety, i.e. a smooth infinite-dimensional manifold
equipped with a privileged vector field. After recalling the definition of
a Lie-Backlund mapping, we say that two systems are equivalent if they
are related by a Lie-Backlund isomorphism. Flat systems are those systems
which are equivalent to a controllable linear one. The interest of
such an abstract setting relies mainly on the fact that the above system
equivalence is interpreted in terms of endogenous dynamic feedback. The
presentation is as elementary as possible and illustrated by the VTOL
aircraft
A survey of differential flatness-based control applied to renewable energy sources
Conference ProceedingsThis paper presents an overview of various methods used
to minimize the fluctuating impacts of power generated from
renewable energy sources. Several sources are considered in the
study (biomass, wind, solar, hydro and geothermal). Different
control methods applied to their control are cited, alongside some
previous applications. Hence, it further elaborates on the adoptive
control principles, of which includes; Load ballast control, dummy
load control, proportional integral and derivative (PID) control,
proportional integral (PI) control, pulse-width modulation (PWM)
control, buck converter control, boost converter control, pitch
angle control, valve control, the rate of river flow at turbine,
bidirectional diffuser-augmented control and differential flatnessbased
controller. These control operations in renewable energy
power generation are mainly based on a steady-state linear control
approach. However, the flatness based control principle has the
ability to resolve the complex control problem of renewable energy
systems while exploiting their linear properties. Using their
flatness properties, feedback control is easily achieved which
allows for optimal/steady output of the system components. This
review paper highlights the benefits that range from better control
techniques for renewable energy systems to established robust grid
(or standalone generations) connections that can bring immense
benefits to their operation and maintenance costs
Flat systems, equivalence and trajectory generation
3rd cycleIntroduction : Control systems are ubiquitous in modern technology. The use of feedback control can be found in systems ranging from simple thermostats that regulate the temperature of a room, to digital engine controllers that govern the operation of engines in cars, ships, and planes, to flight control systems for high performance aircraft. The rapid advances in sensing, computation, and actuation technologies is continuing to drive this trend and the role of control theory in advanced (and even not so advanced) systems is increasing..
A SURVEY ON CONTROL TECHNIQUES OF A BENCHMARKED CONTINUOUS STIRRED TANK REACTOR
The study carried out in this paper unveils a survey on issues related to modelling problems control strategies of a Continuous Stirred Tank Reactor (CSTR), a highly nonlinear plant containing numbers of stable and unstable operating points is considered. The issues discussed are categorised into regulation, feedback linearization, flatness, observation and estimation as well as challenges related to equilibrium points concerning CSTR. In this study, the limited capability of a conventional PID controller is discussed based on preliminary description and a dynamic modelling of the nonlinear plant. Moreover, the limitations of the conventional PID is illustrated through a simulation using nonlinear model of CSTR carried out under input constraint and the presence of bounded disturbances. The result shows that a fixed PID will not guarantee consistent performance throughout operating set points. The feedback linearization formalism is presented to prove that only regulation in the neighbourhood of operating point is possible. Non-minimum phase property exhibited by a CSTR is investigated as well. Flatness control is demonstrated as one of the possible linearization control technique achieving the objective of the trajectory trackin
Robust Model Selection: Flatness-Based Optimal Experimental Design for a Biocatalytic Reaction
Considering the competitive and strongly regulated pharmaceutical industry, mathematical
modeling and process systems engineering might be useful tools for implementing quality by
design (QbD) and quality by control (QbC) strategies for low-cost but high-quality drugs. However,
a crucial task in modeling (bio)pharmaceutical manufacturing processes is the reliable identification
of model candidates from a set of various model hypotheses. To identify the best experimental
design suitable for a reliable model selection and system identification is challenging for nonlinear
(bio)pharmaceutical process models in general. This paper is the first to exploit differential flatness
for model selection problems under uncertainty, and thus translates the model selection problem
to advanced concepts of systems theory and controllability aspects, respectively. Here, the optimal
controls for improved model selection trajectories are expressed analytically with low computational
costs. We further demonstrate the impact of parameter uncertainties on the differential flatness-based
method and provide an effective robustification strategy with the point estimate method for
uncertainty quantification. In a simulation study, we consider a biocatalytic reaction step simulating
the carboligation of aldehydes, where we successfully derive optimal controls for improved model
selection trajectories under uncertainty
Funnel control for a moving water tank
We study tracking control for a moving water tank system, which is modelled
using the Saint-Venant equations. The output is given by the position of the
tank and the control input is the force acting on it. For a given reference
signal, the objective is to achieve that the tracking error evolves within a
prespecified performance funnel. Exploiting recent results in funnel control we
show that it suffices to show that the operator associated with the internal
dynamics of the system is causal, locally Lipschitz continuous and maps bounded
functions to bounded functions. To show these properties we consider the
linearized Saint-Venant equations in an abstract framework and show that it
corresponds to a regular well-posed linear system, where the inverse Laplace
transform of the transfer function defines a measure with bounded total
variation.Comment: 11 page
Disturbance observer design for nonlinear systems represented by input-output models
A new approach to the design of nonlinear disturbance
observers for a class of nonlinear systems described by inputoutput differential equations is presented in this paper. In contrast with established forms of nonlinear disturbance observers,
the most important feature of this new type of disturbance
observer is that only measurement of the output variable is
required, rather than the state variables. An inverse simulation
model is first constructed based on knowledge of the structure
and parameters of a conventional model of the system. The
disturbance can then be estimated by comparing the output of
the inverse model and the input of the original nonlinear system.
Mathematical analysis demonstrates the convergence of this new
form of nonlinear disturbance observer. The approach has been
applied to disturbance estimation for a linear system and a new
form of linear disturbance observer has been developed. The
differences between the proposed linear disturbance observer and
the conventional form of frequency-domain disturbance observer
are discussed through a numerical example. Finally, the nonlinear
disturbance observer design method is illustrated through an
application involving a simulation of a jacketed continuous stirred
tank reactor syste
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