Authors:
Sheila R. Ross,
B. Ross Barmish,
Volume: 1, Page 2756 Paper number 1914
Abstract:
The main result in this paper is a worst-case estimate of the probability
of stability for an uncertain polynomial which has as coefficients
multilinear functions of real, random, independent parameters q_i.
The result requires little apriori information about the probability
distributions of these uncertain parameters. We only require that
the distributions are symmetric about zero, non-increasing as |q_i|
increases, and supported on a given interval [-r_i,r_i]. The probability
estimate is sharp in the sense that the estimated probability of stability
is ^p^*=1 when the uncertainty bounds r_i are below the deterministic
robustness radius r_map obtained with the Mapping Theorem. To obtain
the probabilistic estimate, we recast the problem so that the following
characterization of stability is applicable: If the Nyquist curve for
a proper plant lies to the right of a frequency-dependent separating
line through -1+j0 at each frequency, then stability is guaranteed.
The result is applied in a numerical example, illustrating a common
amplification phenomenon: Even when the magnitude of uncertainty is
significantly greater than the deterministic robustness bound, the
risk of instability is small.
Authors:
Shinji Hara,
Tomoki Miyazato,
Volume: 1, Page 2761 Paper number 9061
Abstract:
A new probabilistic approach to disturbance attenuation problem for
LTI discrete-time systems is proposed. The performance is measured
by a probability with respect to the stochastic noise of which the
worst case 2-norm of the output against a class of deterministic signals
with bounded 2-norm is less than a specified level. We first provides
a matrix inequality characterization of the probability based on the
Toeplitz form of the system and derive a lower bound of the probability.
We then show that a guaranteed performance level can be computed by
solving an LMI convex optimization problem.
Authors:
Takashi Shimomura,
Takao Fujii,
Volume: 1, Page 2763 Paper number 1581
Abstract:
This paper addresses less conservative control design for multiple
design specifications. Although problems are described by a set of
LMIs, they are solved with non-common LMI solutions to reduce the conservatism
arising from seeking a common LMI solution. Noticing that completing
the square can split two variables in BMI terms into two different
LMI ones, we propose iterative algorithms while replacing non-positive
quadratic terms by their upper bounds. A suitable choice of the parameters
in these upper bounds guarantees convergence property. An illustrated
example is included.
Authors:
Scot L. Osburn,
Dennis S. Bernstein,
Volume: 1, Page 2769 Paper number 2177
Abstract:
In this paper we formulate robust stability and performance bounds
in terms of guaranteed cost inequalities. We derive new guaranteed
cost bounds for plants with real structured uncertainty, and we reformulate
them as LMI's. In particular, we obtain a shifted linear bound and
a shifted inverse bound, and give LMI forms for a shifted bounded real
bound, a shifted Popov bound, a shifted linear bound and a shifted
inverse bound. Several examples are used to compare the shifted bounds
with their unshifted counterparts and to make comparisons among these
new bounds and bounds based on standard LMI techniques.
Authors:
Ulf T. Jönsson,
Volume: 1, Page 2775 Paper number 1892
Abstract:
The problem of estimating perturbation bounds for finite trajectories
of non-autonomous systems is considered. A worst case sensitivity derivative
of the trajectory with respect to the uncertainty is used to verify
that the perturbed trajectory is within a given neighborhood of the
nominal. This gives rise to a robust control problem for linear time-varying
systems. It is shown that relaxation using integral quadratic constraints
and the solution to a linear quadratic optimal control problem can
be used to find bounds on the robust control problem.
Authors:
Mauricio C. de Oliveira,
Juan F. Camino,
Robert E. Skelton,
Volume: 1, Page 2781 Paper number 2101
Abstract:
This paper addresses the design of linear controllers with special
structure imposed on the gain matrix. This problem is called a SLC
(Structured Linear Control) problem. The SLC problem includes fixed
order output feedback control, decentralized control, joint plant and
control design, and many other linear control problems. A theoretical
framework that allows one to pursue the solution of SLC problems is
provided. Although the obtained conditions are nonconvex, it is shown
that solving a SLC problem involving standard control objectives such
as stability, bounds on the H_2 or H_(infinity) norms, and real positiveness
is not harder than solving a standard unstructured static output feedback
problem. A convexifying algorithm that might be used to solve the
SLC problem is also developed. At each iteration a certain function
is added to the constraints in order to make them convex. At convergence,
the artificially introduced convexifying functions reduce to zero,
guaranteeing the feasibility of the original problem. Local optimality
can be guaranteed. Some examples illustrate how the SLC framework
and the convexifying algorithm can improve the solutions of control
problem with suboptimal solutions available.
Authors:
Paulo C. Pellanda,
Pierre Apkarian,
Daniel Alazard,
Volume: 1, Page 2787 Paper number 1151
Abstract:
The dynamic behavior of gain-scheduling controllers is highly depending
on the state-space representations adopted for the family of linear
controllers designed on a set of operating conditions. In this paper,
a technique for determining a set of consistent and physically motivated
linear state-space transformations to be applied to the original set
of linear controllers is proposed. After transformation, these controllers
exhibit an observer-based structure and are therefore easily interpolated
and implemented. This method is applicable to discrete- or continuous-time
and full- or augmented-order compensators, particularly including H_(infinity)
and µ controllers, which do not generally enjoy ease of implementation.
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