Design and simulation of a combined serpentine t-shape magnetorheological brake

Abstract

A magnetorheological brake (MRB) is a device to dissipate rotational energy using magnetorheological fluids (MRF). MRB can change its braking torque quickly in response to external magnetic field strength. The brake is rotational, utilizing the MRF in shear mode. In this study, the geometrical design of the MRB, magnetic circuit and MRF flow path is addressed. Mathematical models are presented that describe the braking torque of the MRB. A novel prototype is introduced combining T-shape rotor model with serpentine flux magnetic circuit configuration. The rotor member is selected to direct the flux concentration at that location. Serpentine flux configuration is selected to achieve higher torque without increasing the size of MRB by activated more surface area of MRF with the magnetic flux. The finite element method is used to evaluate the magnetic flux density in MRB using FEMM 4.2. FEMM results showed that this novel design could provide sufficient magnetic flux along MRF flow path. Finally, the influence of input current to the MRB on braking torque is investigated. It is found that the braking torque in MRB increases with the increase of the input current. The prototype is formulated as foot-drop prevention orthotic. The MRB would be further integrated into ankle-foot orthoses for post-stroke patients. The design is formulated as a preliminary geometrical design, aiming to obtain the minimum required braking torque.

Characterization of T-shaped magneto-rheological brake

“…The materials would also affect magnetic flux density. It could be seen at the difference of magnetic flux density result from this research and Hidayatullah et al [14].…”

“…The usage of smaller wire diameter could add more turn that would generate more magnetic flux. On FEMM result, maximum magnetic flux density was 0.45 T. It is bigger than Ubaidillah et al [7], but smaller than Hidayatullah et al [14] and Nguyen et al [16]. Some factors could affect the result.…”

“…This new design of MRB T-shaped had more compact structure than Hidayatullah et al [14] with a smaller design. It would give patient installing MRB in the foot orthosis more freely.…”

“…Another earlier T-shape MRB was made based on those previous T-shape design, it is found that to reach a good and effective magnetization area in the MRB, usually, they took more than 1 coil for magnetic flux generator. For example, Nguyen and Choi [14] had made MRB T-shaped with two coils. It would be consuming more power due to the needs of multi-coil.…”

Improving Passive Ankle Foot Orthosis System Using Estimated Ankle Velocity Reference

“…An MR brake at the ankle joint generates controllable damping stiffness [23], [24]. The MR brake is a T-shape brake [25], where the gap is filled with MR fluid LORD-132DG. The MR brake is powered using an external power supply.…”