A tuner that accelerates parameters

We propose a tuner, suitable for adaptive control and (in its discrete-time version) adaptive filtering applications, that sets the second derivative of the parameter estimates rather than the first derivative as is done in the overwhelming majority of the literature.     

A smoothly parameterized family of stabilizable, observable linearsystems containing realizations of all transfer functions of McMillandegree not exceeding n

It is shown that there is a continuously parameterized family F of n-dimensional single-input single-output (SISO) stabilizable detectable linear system Σ(p) which contains at least one realization of each reduced, strictly proper transfer function of McMillan degree not exceeding n. The parameterization map p→Σ(p) is a polynomial function in 2n indeterminates from an open convex polyhedron in R²ⁿ to the linear space of all SISO n-dimensional linear systems     

MIMO design models and internal regulators for cyclicly switchedparameter-adaptive control systems

In Pait and Morse (1994) the concept of “cyclic switching” was proposed as a means of dealing with the well-known stabilizability problem, which arises in adaptive controller synthesis because of the existence of points in parameter space where the design model upon which certainty equivalence control is based loses stabilizability. While the procedure outlined in the above paper is specific enough to enable one to construct cyclicly switched adaptive controllers for SISO process models, for the MIMO case two key issues are left unresolved. The objective of this paper is to address both of these issues, thereby extending excitation free, identifier-based adaptive control methods to minimum and nonminimum phase MIMO linear systems     

The suboccipital cavernous sinus

The authors studied the microsurgical anatomy of the suboccipital region, concentrating on the third segment (V3) of the vertebral artery (VA), which extends from the transverse foramen of the axis to the dural penetration of the VA, paying particular attention to its loops, branches, supporting fibrous rings, adjacent nerves, and surrounding venous structures. Ten cadaver heads (20 sides) were fixed in formalin, their blood vessels were perfused with colored silicone rubber, and they were dissected under magnification. The authors subdivided the V3 into two parts, the horizontal (V3h) and the vertical (V3v), and studied the anatomical structures topographically, from the superficial to the deep tissues. In two additional specimens, serial histological sections were acquired through the V3 and its encircling elements to elucidate their cross-sectional anatomy. Measurements of surgically and clinically important features were obtained with the aid of an operating microscope. This study reveals an astonishing anatomical resemblance between the suboccipital complex and the cavernous sinus, as follows: venous cushioning; anatomical properties of the V3 and those of the petrous-cavernous internal carotid artery (ICA), namely their loops, branches, supporting fibrous rings, and periarterial autonomic neural plexus; adjacent nerves; and skull base locations. Likewise, a review of the literature showed a related embryological development and functional and pathological features, as well as similar transitional patterns in the arterial walls of the V3 and the petrous-cavernous ICA. Hence, due to its similarity to the cavernous sinus, this suboccipital complex is here named the "suboccipital cavernous sinus." Its role in physiological and pathological conditions as they pertain to various clinical and surgical implications is also discussed.     

Geometry of adaptive control: optimization and geodesics

Two incompatible topologies appear in the study of adaptive systems: the graph topology in control design, and the coefficient topology in system identification. Their incompatibility is manifest in the stabilization problem of adaptive control. We argue that this problem can be approached by changing the geometry of the sets of control systems under consideration: estimating n_p parameters in an n_p‐dimensional manifold whose points all correspond to stabilizable systems. One way to construct the manifold is using the properties of the algebraic Riccati equation. Parameter estimation can be approached as an optimal control problem akin to the deterministic Kalman filter, leading to algorithms that can be used in conjunction with standard observers and controllers to construct stable adaptive systems. Copyright © 2004 John Wiley & Sons, Ltd.     

Muscle and musculocutaneous flap coverage of exposed spinal fusion devices

Midline wound dehiscence in the back with exposure of spinal stabilization devices remains a challenging problem, mainly in the presence of infection. Usually, the treatment consists of instrumentation removal, wound debridement, and antibiotic therapy. These can result in instability of the spine and significantly prolong the hospitalization. The use of muscle and musculocutaneous flaps provides excellent soft-tissue coverage, obliterates the dead space, controls the infection, and creates conditions to salvage the hardware. Eight cases of spinal rod instrumentation, complicated by wound infection and dehiscence, have been treated successfully with single or multiple muscles and musculocutaneous flaps. Our method of treatment for these complex wounds, in two institutions, is discussed.     

A cyclic switching strategy for parameter-adaptive control

This paper introduces a new strategy, called “cyclic switching,” to deal with the well-known certainty equivalence control synthesis problem which arises in the design of identifier-based adaptive controllers because of the existence of points in parameter space where the design model Σ_D, upon which certainty equivalence synthesis is based, loses stabilizability. Unlike most previously suggested methods for handling this problem, the technique proposed here can be employed with or without process excitation. For the technique to work it is not necessary for there to be a mechanism for moving tuned parameters away from values at which Σ_D loses stabilizability, and no such mechanism is used