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PubMed1990

Regulating knee joint position by combining electrical stimulation with a controllable friction brake.

Hybrid FES gait restoration systems which combine stimulation with controllable mechanical damping elements at the joints show promise for providing good control of limb motion despite variations in muscle properties. In this paper we compared three controllers for position tracking of the free swinging shank in able-bodied subjects. The controllers were open-loop (OL), proportional-derivative closed-loop (PD), and bang-bang plus controlled-brake control (CB). Both OL and PD controllers contained a forward path element, which inverted a model of the electrically stimulated muscle and limb system. The CB control was achieved by maximally activating the appropriate muscle group and controlling the brake to be a "moving-wall" against which the limb pushed. The CB control resulted in superior tracking performance for a wide range of position tracking tasks and muscle fatigue states but required no calibration or knowledge of muscle properties. The disadvantages of CB control include excess mechanical power dissipation in the brake and impact forces applied to the skeletal system.

Biomechanical Phenomena↗
PubMedDate not supplied

A new guidewire with kink-resistant core and low-friction coating.

A new guidewire constructed from kink-resistant titanium-nickel alloy, polyurethane, and hydrophilic polymer is described. We have used this wire in 119 angiographic and 49 interventional procedures without complications. In numerous applications, it offers significant advantages over other guidewires. It is particularly helpful for angiography and interventional procedures requiring catheterization through markedly tortuous vessels, tight stenoses, or occlusions.

Alloys↗