Affiliations: [a] Department of Mechanical Engineering, National Cheng
Kung University, Tainan, Taiwan
Correspondence:
[*]
Corresponding author: Nan-Chyuan Tsai, Department of Mechanical
Engineering, National Cheng Kung University, Tainan City 70101, Taiwan. Tel.:
+886 6275 7575 Ext. 62137; Fax: +886 6236 9567; E-mail:
nortren@mail.ncku.edu.tw
Abstract: A TDOF (Two Degrees of Freedom) Servo Gap-Retained Mechanism (SGRM)
is proposed and verified by experiments in this work. It mainly consists of a
flywheel and an Intelligent Posture Tracking System (IPTS). The flywheel,
driven by an induction motor for spinning, is regarded as the tracking
objective of the IPTS. The IPTS is mainly composed by an intelligent disc and
the Hybrid Magnetic Actuators (HMAs). The posture of the intelligent disc is
controlled by the magnetic forces induced by the HMAs to retain a constant gap
with respect to the eccentric flywheel which spins, tilts and wobbles. Since
the HMA is highly nonlinear, a Feedback-Linearized Sliding Mode Control (FLSMC)
is synthesized to account for system parameter nonlinearities or unmodeled
dynamics. The dynamics of the flywheel and the IPTS are theoretically
investigated and analyzed. In fact, the proposed SGRM is a part of an entire
flywheel cell. That is, once the MGU (Motor/Generator Unit) in flywheel cell
operates at idle mode, the shaft of flywheel will be separated apart from MGU
in order to avoid the energy loss of the flywheel by the back EMF induced by
the magnetic field of MGU. On the other hand, the shaft of flywheel and MGU
still need to maintain synchronous power transmission even at idle mode so that
a non-contact clutch is equipped. Generally speaking, the role of SGRM in a
flywheel cell is to ensure the centerline of the flywheel properly aligned with
the non-contact clutch. At last, intensive computer and experimental
simulations are undertaken to verify the feasibility of the proposed SGRM and
FLSMC. It is evidently showed that the proposed SGRM under FLSMC exhibits
superior transient response and servo capability upon constant gap retained.
The steady-state tracking errors are about 5% with respect to the amplitudes of
the reference trajectories in two radial directions (i.e., X-axis and Y-axis).
Keywords: Servo gap-retained mechanism, hybrid magnetic actuator, feedback-linearized sliding mode control
