1,720,992 research outputs found
Stability analysis and guaranteed cost control for stochastic nonlinear quadratic systems
No full textIn this paper we extend the guaranteed cost
control approach for nonlinear quadratic systems (NLQSs),
developed by the same authors in some recent papers, to the
stochastic framework. In particular, we consider a stochastic
NLQS in the Itˆo’s form and provide a sufficient condition for
the existence of a state feedback controller guaranteeing, with
a certain risk factor a 2 [0;1), that the closed loop system
satisfies, for any initial condition belonging to a given polytopic
set, an assigned bound for a given quadratic cost; the condition
requires to solve a feasibility problem constrained by linear
matrix inequalities. The proposed theory is then illustrated by
an example concerning the design of optimal strategies for the
removal of malicious software in computer networks
A parsimonious friction model for efficient identification and compensation of hysteresis with non-local memory
No full textA novel dynamic friction model, which allows to capture friction hysteresis with
non-local memory, is presented in this paper. The model is conceived in order to find a trade-off
between accuracy of the model prediction and difficulty of implementation in motion control
systems with model-based friction compensation. The hysteresis function introduced into the
model accounts for non-local memory, i.e., the property for which the friction output depends not
only on the initial conditions but also on past extremum values of the input or the output. In
comparison with other models incorporating a hysteresis function with non-local memory, the
proposed model is demonstrated to reduce the number of parameters necessary to reproduce the
hysteresis loops observed experimentally. Moreover, parameter identification can benefit from
the availability of a closed form of the model solution
Control of a three-wheeled omnidirectional mobile robot via a mixed FTB/ approach
No full textIn this paper, the problem of guidance and motion control of mobile robots is addressed and solved within the novel framework
of the mixed finite-time/H∞ control theory of nonlinear quadratic systems (NLQSs). Starting from a NLQS describing
the dynamics of omnidirectional mobile platforms, the main tasks performed for controlling in closed loop the motion
of omnidirectional robots can be conveniently formulated as a mixed finite-time/H∞ control problem. A robust motion
controller, which can effectively rejects disturbances deviating the robot platform from a planned path, can be designed
after choosing a linear state-feedback structure for the controller. The synthesis problem is solved through some sufficient
conditions contemplating both norm-bounded disturbances and sets constraining initial and terminal conditions, together
with a finite-time bound on the output transient. Therefore, for all the allowable uncertainties, in presence of nonzero initial
conditions and exogenous disturbance inputs which are possible within an unstructured environment, the motion control
tasks can be accomplished through optimal H∞ performance by simultaneously guaranteeing that the NLQS, which governs
in closed loop the robot platform, is finite-time bounded. Finally, the applicability and control performance of the design
approach have been evaluated through numerical simulations
Stabilization of bilinear systems via linear state feedback control
No full textIn this paper we consider the problem of
stabilizing a bilinear system via linear state feedback control.
A procedure is proposed which, given a polytope P
surrounding the origin of the state space, nds, if existing,
a controller in the form u = Kx, such that the zero
equilibrium point of the closed loop system is asymptotically
stable and P is enclosed into the domain of attraction of
the equilibrium. The controller design requires the solution
of a convex optimization problem involving Linear Matrix
Inequalities. An example illustrates the applicability of the
proposed technique
Identification and modelling of the friction-induced hysteresis in pneumatic actuators for biomimetic robots
No full textPneumatic Artificial Muscle (PAM) is becoming
one of the most used actuator technology for the development
of biorobotic applications, such as robotic orthoses and
wearable exoskeletons, which require the accurate control of
the impedance during human-robot interactions. Although the
adaptable compliance of PAMs is desirable, the nonlinear and
hysteretic relation between contraction length and pulling force,
as well as the air pressure within the chamber of the PAM, make
difficult the identification and the control of the dynamics of
such actuators.
After the description of the experimental setup designed for
the dynamic identification of PAMs, this paper presents a novel
and accurate model of the hysteresis of the mechanical response
of PAMs. Some experimental tests have been performed on
a real pneumatic muscle in order to reproduce the different
features of the hysteretic behavior which are taken into account
in the definition of the model.
The proposed model, which has been validated through some
experiments, provides some advantages in terms of ease of
parameter identification and implementation into a control
system, thanks to the use of a limited number of parameters.
Index Terms—friction identification and compensation, hysteresis
with nonlocal memory, pneumatic artificial muscles
A synthetic biology approach to the realization of embedded feedback controllers for Chemical Reaction Networks
No full textChemical Reaction Network (CRN) models based on the mass-action law play an important role in the life sciences, since they can be used to describe dynamical processes of interest in many fields of chemistry and biology. A fundamental challenge related to this kind of systems is represented by the lack, within the framework of Systems and Synthetic Biology, of a general methodology to design control systems for CRNs. The main issue addressed by this work is the development of a general methodology for designing embedded feedback control schemes for an assigned CRN, i.e. controllers that are themselves realizable through a CRN. In particular, we illustrate the effectiveness of the proposed approach by designing a proportional feedback controller for a well-characterized biochemical system
Guaranteed cost control for uncertain nonlinear quadratic systems
No full textThe problem of the robust and optimal control for
uncertain quadratic systems is dealt with in this paper.
Resorting to a guaranteed cost approach, this paper proposes
a novel control design methodology which enables to find a state
feedback controller guaranteeing for the closed-loop system: i)
the local asymptotic stability of the zero equilibrium point; ii)
the inclusion of a given polytopic region into the domain of
attraction of the zero equilibrium point; iii) the satisfaction
of a quadratic performance index. The control performance is
guaranteed against parametric uncertainties which are assumed
to be norm-bounded.
This design procedure involves the solution of a Linear
Matrix Inequalities (LMIs) optimization problem, which can
be efficiently solved via off-the-shelf algorithms. An example,
concerning an application of motion control for robotic arms,
shows the effectiveness of the proposed methodology
Robust control of quadratic systems with norm bounded uncertainties
No full textThis paper deals with the problem of the stabilization
of uncertain quadratic systems via state feedback. The
main contribution of the paper is a control design methodology
which enables to find a robust controller guaranteeing for
the closed-loop system: i) the local asymptotic stability of the
zero equilibrium point; ii) the inclusion of a given polytopic
region into the domain of attraction of the zero equilibrium
point. This design procedure involves the solution of a Linear
Matrix Inequalities (LMIs) feasibility problem, which can
be efficiently solved via available optimization algorithms. A
numerical example shows the effectiveness of the proposed
methodology
Model-based tracking control design, implementation of embedded digital controller and testing of a biomechatronic device for robotic rehabilitation
No full textIn this paper, the tracking control problem of a biomimetic exoskeleton powered by a pair of pneumatic artificial
muscles is considered. The antagonistic configuration of the pair of pneumatic muscles, which is biologically
inspired, enables safe and reliable actuation in applications of orthopaedic rehabilitation. However, during the
inflation-deflation process, the pneumatic muscles introduce nonlinearity and hysteresis which deteriorate the
control performance. A model of the antagonistic artificial muscles is adopted to develop a computed-torque
control for feedforward compensation of the nonlinear dynamics of the actuated joint. A PID control action is
used in combination with the feedforward compensation to achieve fast and accurate tracking control performance.
The model, which possesses a reduced set of parameters as functions of the inflation/deflation phase,
enables efficient nonlinear compensation. The experimental tests on the biomechatronic device, compared with
other state-of-the-art approaches for controlling pneumatic artificial muscles, show better tracking performance
in terms of convergence rate and robustness, justifying the convenience of using the proposed control methodology
in the design of tracking controllers for exoskeletal biomechatronic devices
Optimal guaranteed cost control of a biomimetic robot arm
No full textIn this paper, an optimal control problem for
uncertain bilinear systems is formulated via a guaranteed cost
approach and then applied to the design of a stabilizing controller
for a robot arm actuated by Pneumatic Artificial Muscles
(PAMs). The results show that the contributed methodology
is suitable for efficiently designing control systems which can
match the requirements both on safety and on energy efficiency
for PAMs-driven robots during human-robot interactions. The
performances of the state-feedback control system are evaluated
on the basis of some numerical simulations
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