Six degree of freedom quasi-zero stiffness magnetic spring with active control: Theoretical analysis of passive versus active stability for vibration isolation

This paper presents a comparison of passive and active stability analyses of a six degree of freedom (DOF) quasi-zero stiffness magnetic levitation vibration isolation system. The passive rotational stability of the system is varied by changing lever arms, and its effects on the vibration isolation...

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Bibliographic Details
Published in:Journal of sound and vibration 2021-06, Vol.502, p.116086, Article 116086
Main Authors: Kamaruzaman, Nur Afifah, Robertson, William S.P., Ghayesh, Mergen H., Cazzolato, Benjamin S., Zander, Anthony C.
Format: Article
Language:English
Subjects:
Active control
Actuation
Closed loop systems
Control stability
Control systems design
Cross coupling
Decentralized control
Degrees of freedom
Error analysis
Magnetic fields
Magnetic levitation
Noise measurement
Optimal control
Quasi-zero stiffness
Robust control
Simulation
Six DOF
Stability
Stability analysis
Stiffness
Systems stability
Vibration
Vibration analysis
Vibration control
Vibration isolation
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Summary:This paper presents a comparison of passive and active stability analyses of a six degree of freedom (DOF) quasi-zero stiffness magnetic levitation vibration isolation system. The passive rotational stability of the system is varied by changing lever arms, and its effects on the vibration isolation performance and control cost are investigated via static and dynamic simulations. The practicality of the design is also discussed by simulating off-centred load scenarios. It is shown that the vibration isolation bandwidth reduces with increasing passive stiffness when such (passively) stable DOFs are close to being uncontrolled, and that the passively unstable rotational DOF benefits from an optimal control action. In practice, the effect of increasing the passive stability on the isolation performance is insignificant as the controller would typically be designed with a relatively large stability margin to account for uncertainties, thus dominating the closed-loop response. In contrast, the control does benefit from the improved passive stability. The robustness of the designed control system to probable time delay, sensor measurement noise, and actuation error is simulated and verified. Additionally, the importance of taking cross-coupling into consideration when designing a stabilising control through a decentralised control scheme is highlighted.
ISSN:0022-460X
1095-8568
DOI:10.1016/j.jsv.2021.116086