Study of a magnetorheological brake under compression-shear mode

Abstract

A magnetorheological (MR) brake under compression-shear mode is designed, simulated and experimentally investigated in this paper. A MR brake under compression-shear mode was first designed considering compression enhanced shear yield stress of MR fluid. Then, the operating principle of the MR brake was illustrated and mathematical torque expressions, operating under compression-shear mode assuming Herschel-Bulkley model, was further established. Moreover, simulation analysis of the designed magnetic circuit was performed as well. An experimental prototype was fabricated and tested to evaluate the transmission performance of MR brake. The results showed that the large torque could be produced at high applied currents, high compressive stress, large compressive strain and small initial gap distances. The rotational speed and compressive speed had little effect on the torque. The characteristic rising time of the torque was greatly affected by the rotational speed, the compressive strain, and compressive speed. However, the current had little effect on the rising time. The time constant would became shorter when both the rotational speed and the compressive speed were faster. Through analyzing the compression of particle chains in MR fluids directly, it was found that the diameter and the length of the particles chains brought a strong influence on the essential property of MR fluids under compression. Thus, the compressive stress or compressive strain and the initial gap distance also played an important role in enhancing the torque. The results also showed that the proposed MR brake could generate a maximum torque of 241 Nm, about 17.9 times the magnitude of braking torque without compression, and achieve a high torque density of 125.6 kN m -2 and a time constant of 58 ms. This study provides a better understanding of MR brake under compression-shear mode and the implications for many high-power applications.

A Review on Structural Configurations of Magnetorheological Fluid Based Devices Reported in 2018–2020

“…(C) High-torque squeezing MRF brake (Wang et al, 2019a). (D) MRF brake with squeeze-shear mode (Wang and Bi, 2020). (E) Snake like robot with MRF actuators (Zhang D. et al, 2020).…”

“…performance, and a magnetic vane was set to ensure that a magnetic flux crosses both sides of the rotor, shown in Figure 4D (Wang and Bi, 2020). Utilizing the combined mode, the MRF device generated higher torque compared to those without compression.…”

Transient behavior of compressed magnetorheological brake excited by step currents

“…Despite the fact that MR brakes have been investigated repeatedly under compression-shear, many of the studies dealt with the stable characteristics of MR brakes under constant currents 19 – 23 , as briefly noted here. Patil et al have experimentally studied the influencing parameters of braking torque of MR brake in shear and squeeze mode 19 .…”

Performance Analysis of Rotary Magnetorheological Brake With Multiple Fluid Flow Channels

“…Nguyen et al [24] designed a multi-pole MR brake, which adopts multiple excitation coils evenly arranged to form multiple magnetic poles, further enhance the braking torque of the drum brake. Wang and Bi [25] designed a MR brake with compression shear mode. Under the conditions of high pressure and small damping gap, the braking torque was significantly improved.…”