Title:
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Optimization Over Symmetric Positive Semidefinite Matrices Using Conical Hulls
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The research. concerns the development of algorithms for solving convex
optimization problems over the set of symmetric positive semidefinite (PSD) matrices.
The iterative algorithms developed here are b~ed on the characterization of the PSD set
as a cone and the representation of constrainea sets as linearly-mapped PSD cones. The
feasible set for a certain problem can be represented as the intersection of various cones
and the problem is transformed into a norm minimization problem.
To solve the problem, the notion of the supporting hyperplane of the PSD cone is
introduced. The contact points of the hyperplanes with the corresponding cones
determine the set within which the solution will be computed iteratively. Two approaches
will be used in forming the solution set. '
The first approach uses the contact point for defining a search line as the set on
. which a quadratic problem is solved to obtain the minimizer. In the second approach, the
contact points are used to form a conical hull as the approximation of the solution set
over which the quadratic problem is solved.
The approach is then applied in the study of the stability of a multi-configurations
system, that is for finding a common quadratic Lyapunov function (eLF) of a family of
stable linear systems. Further the proposed algorithm is investigated for the case of
minimization over the jntersection of cones. The numerical results suggest that the
proposed algorithm can perform moderately well for some cases, compared to the
projective method.
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