1,721,023 research outputs found
Stability and control of transversal oscillations of a tethered satellite system
No full textThe tethered satellite system is characterized by weak nonlinearities but it practically works in conditions of internal resonance which produces unstable oscillations. The effect of a longitudinal control force is investigated. Since the displacement component in the orbit plane is always present in the motion due to the nonlinear coupling, the control force is assumed depending only on this component and also when a prevailing out-of-plane oscillation is considered. The harmonic balance method and numerical solutions of amplitude modulated equations are used to obtain stationary and nonstationary oscillations, respectively; the Floquet theory is followed in the stability analysis. The assumed control force is shown to be effective in reducing the primary and secondary instability regions of oscillations perturbed by internally resonant disturbance components
A 0.23 μ, 96 mV Input Voltage DC-DC Converter for Body Sensor Nodes
No full textThis paper presents an ultra-low power DC-DC converter to be embedded into body sensor nodes. The proposed DC-DC converter is used to step-up the voltage at the output of a micro-thermoelectric generator up to a usable supply voltage between 0.42 and 1.05 V. Measurements have been conducted on ten available samples. The resulting mean value of the minimum input voltage is 96 mV. At the minimum input voltage, the power consumption is only 0.23 . The operating temperature ranges from -40 °C to 100 °C
Stability and bifurcations of transversal motions of an orbiting string with a longitudinal force
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Active longitudinal control of wind-induced oscillations of a suspended cable
No full textActive control of oscillations of a suspended cable under transversal wind, described by a constant term and a fluctuating turbulent component, is dealt with. Control of transversal in-plane and out-of-plane oscillations is performed by imposing a longitudinal motion to one support; the control law depends, linearly or quadratically, on measures of displacement and velocity of a selected point. First, the steady-state oscillations around the planar static configuration, determined by the wind constant component, under sinusoidal in-plane and out-of-plane loading are studied, showing the nonlinear behaviour in the regions of primary and parametric resonance and the effects of the control action. Afterwards, attention is focused on the response of the cable to transversal wind turbulence, whose fluctuating component is described by a random process with an assigned spectral density. The effectiveness of longitudinal control is analysed by means of numerical investigations
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