Hysteresis Nutation Damper for Spin Satellite

Hysteresis dampers are commonly used in Passive magnetic Attitude Control System (PACS). In PACS these rods produce a damping torque and reduce the satellite angular momentum and angular velocity. In this paper, a spin satellite was investigated which utilizes a passive magnetic damper consisting of magnetic hysteresis rods aligned with principal axis or spin axis of satellite and de-tumbling of the satellite, and the pure spin was achieved. An analytical model was presented to analyze hysteresis damper and a numerical simulation was performed to obtain dynamic properties of the spin attitude. In addition, assuming a dynamic imbalance, attitude behavior and damper effect on the spin rate of satellite were analyzed. The behavior of this passive magnetic stabilized satellite was simulated from the initial post separation phase.

Nutation Damper Undergoing a Coupled Motion

A novel numerical model is proposed to simulate liquid sloshing in a rectangular nutation damper (i.e. a tuned liquid damper) undergoing a coupled horizontal and rotational motion. Shallow water theory is used consistently to derive the governing equations of motion so that the model is applicable to large sloshing involving a hydraulic jump. It can also accommodate exposure of part of the damper’s floor to air by using a somewhat improved boundary shear approximation. A simple finite difference approach – the Lax scheme – is found to solve the equations of motion surprisingly well. Numerical predictions are checked against limited experimental data for a purely horizontal motion. Good agreement is generally observed. Furthermore, to demonstrate the model’s broader scope, the effect of a rotation is also considered in conjunction with a horizontal motion. The rotation is shown to significantly enhance the damper’s energy dissipation and, hence, its attenuation capability. For convenient practical application, an equivalent singledegree-of-freedom oscillator model is presented to characterize a nutation damper’s behavior for a coupled motion. The equivalent parameters of the model are determined so that the dissipated energy “best” fits a numerical counterpart. Their effect is investigated for different lengths, depths, and vibration levels of the damper. While the motivation of this investigation is to control the wind-induced galloping of overhead power lines, the proposed approach is applicable more generally to any excitation that induces low frequency vibrations.

Behavior of a Nutation Damper Undergoing a Coupled Horizontal/Rotational Motion

Shallow water theory is used to describe the sloshing and severe wave breaking action of water contained in a rigid nutation damper undergoing a coupled horizontal/rotational motion. Results from a simple numerical procedure are shown to agree with limited experimental data. They also demonstrate that a nutation damper’s rotation promotes a hydraulic jump that beneficially enhances damping.