Effect of sinusoidal base motion on a magnetic bearing

Abstract

Many of the proposed applications for magnetic bearings involve their use in moving vehicles. These include flywheels for energy storage in terrestrial applications, such as buses and trains, and also in space-based applications, such as satellites. Most of the existing research literature on magnetic bearings is for static systems where the base is stationary. For vehicular applications, magnetic bearings will be subject to base motion that will have significant effects on the dynamics. In addition, magnetic bearings designed for vehicle use are expected to be power-limited, which leads to decreased stiffness and damping. The implications of these effects on the design of active magnetic bearing systems are significant but have not been fully investigated. In order to address the base motion scenario, a small non-rotating test rig with a single magnetic bearing mounted on a shaker has been built and tested to study the effect of sinusoidal base motion on the magnetic bearing's ability to support a target mass. The tests include base excitation of the system at different frequencies and amplitudes including the natural frequency of the system. Results from this test rig for three cases of bearing stiffness and damping properties are presented. Test results show both linear and non-linear behavior for the cases of bearing stifmess and damping tested. The tests also demonstrate the implications associated with the requested level of stiffness and damping on limiting the operating performance range of the magnetic bearing undergoing sinusoidal base motion.

Acceleration feedforward control in active magnetic bearing system subject to base motion by filtered-X LMS algorithm

“…The magnetic force is approximately proportional to the square of the coil current and inversely proportional to the square of the gap as follows: (4) where is the shape factor, is the permeability H/m , is the area of one pole, is the number of turns of coil, is the bias current, and is the control current.…”

“…Kasada [4] also demonstrated the implications of feedback control in the context of the requested level of stiffness and damping. A controller with a wider bandwidth, however, often induces a mechanical resonance.…”

Sliding mode control for an active magnetic bearing system subject to base motion

“…The most commonly used controls on this subject are feedback control [3,4], disturbance feedforward compensation [2,5], nonlinear control [6] and sliding mode control (SMC) [7][8][9][10][11][12]. In an AMB system, feedback control is necessary to stabilize the system, and higher gain provides greater disturbance attenuation.…”

“…The advantages include elimination of a lubrication system, friction free operation, low power loss, and controllability of bearing dynamic characteristics [3][4][5].…”

Test of base vibration influence on dynamics of a magnetic suspended disk

“…M. E. Kasarda and etc. discussed effect of sinusoidal base motion on a magnetic bearing though experiments, which provides valuable reference to this paper [9].…”