This article presents a new design of a multi-pole magnetorheological (MR) clutch, with a hybrid magnetization using several permanent magnets and several excitation coils. The permanent magnets are used as the first source of generating the magnetic field, and the excitation coils are used to adjust the magnetic field to the required value. Firstly, a detailed illustration of the mechanical design of the MR clutch is presented. The principal design parameters of the proposed clutch are determined to achieve maximum torque according to the magnetic circuit. After that, the torque model is established, and simulations are conducted to evaluate the magnetic circuit design. Subsequently, an experimental set-up is established, and the proposed MR clutch is designed and manufactured, and a series of experiments are carried out. The results clearly show that different torque output can be obtained by controlling the current magnitude and direction of each coil. Finally, to achieve a precise feedback torque control, the design of a current controller is carried out using conventional proportional-integral-derivative (PID) control scheme. The results demonstrate that the designed PID controller can be used to obtain the desired torque.

This paper studies on the permanent magnets configuration on the transmission torque of the multi-pole bilayer magnetorheological (MR) coupling. Based on the electromagnetic field theory, the magnetic circuit models of traditional permanent magnet array (TPMA) and Halbach permanent magnet array (HPMA) are established, and the magnetic flux density within the MR fluid working gaps has been derived in order to evaluate the merits of the designed MR coupling. A 3D FE magnetic-fluid analysis has been necessary following the initial conceptual analysis, in order to study the influence of key parameters on the transmission torque. The results show that the transmission torque of the MR coupling with Halbach permanent magnet array is 33.45% higher than that of the ordinary permanent magnet array, with a same structure size. For the MR coupling with Halbach permanent magnet array, the unilateral magnetic focusing effect is better with the increase of the residual flux density of the secondary magnetic pole as well as the radial length of magnetic pole. And the single side magnetic focusing effect is the best when the main magnetic pole is 15°. The influence of the magnetic pole angle on the transmission torque has been further studied.

Background To explore the role of anti-Mullerian hormone (AMH) in predicting the need to step up recombinant FSH (rFSH) dose in IVF/ICSI cycles of polycystic ovarian syndrome (PCOS) women. Methods This is a retrospective cohort study of 825 PCOS related infertility enrolled from Jan 2019 to Dec 2021. The daily rFSH dose at which the first response to rFSH were recorded. The dose at which the first response to rFSH was based on folliculometry during follow up in which two or more follicles reached ≥ 11mm. A receiver operating characteristic (ROC) curve analysis was done to investigate the ability of AMH to predict the need to step up initial rFSH dose. Results PCOS women who needed to step up initial rFSH dose had a significantly higher AMH compared with those didn’t step up initial rFSH dose (11.37 ± 3.25ng/ml vs. 8.69 ± 3.16ng/ml, P < 0.001). In multivariate logistic regression analysis, increased AMH level was an independent factor for the need to step up initial rFSH dose in PCOS patients after adjusted for confounding factors. ROC curve analysis showed AMH could predict the need to step up initial rFSH dose (AUC = 0.738, 95%CI: 0.704–0.773), having 75.4% specificity and 63% sensitivity when the threshold AMH concentration was 9.30ng/ml. 58.8% PCOS women with AMH > 9.30 ng/ml required increased rFSH dose compared to 18.8% of women with AMH ≤ 9.30ng/ml (p < 0.001). Although the clinical pregnancy rate and live birth rate were not significantly different, there was a higher incidence of OHSS among women with AMH > 9.30 ng/ml vs. AMH ≤ 9.30ng/ml (20.8% vs. 15.3%, p = 0.043). Conclusion PCOS women with AMH > 9.30 ng/ml were resistant to rFSH stimulation and require increased dose for the cycle recruitment of ovarian follicles.