Consideration of centrifugal effect in torque estimation for disc-type MR devices

Abstract

In order to design high performance magnetorheological (MR) devices, an accurate force/torque estimation for MR devices is greatly significant. This work presents a method for torque estimation with consideration of centrifugal effect (CE) for disc-type MR devices. A modified magnetorheological fluid (MRF) constitutive model is proposed to introduce the radial stress for analyzing the CE. With the modified constitutive model, the radial dynamics about CE is considered in the MRF governing equations. Comparing to the traditional MRF flow description, which only includes the circumferential dynamics, the new flow equations is extended to consider both circumferential and radial dynamics by integrating the radial equilibrium and circumferential equilibrium. Then, an extra boundary condition for radial stress is assumed to solve the equations based on the analysis of CE. The torque is obtained by integrating the circumferential stress acted on the rotor surface, which is determined by the flow governing equations. To analyze the applicability of the torque estimation method, a critical velocity is defined for analyzing the conditions of centrifugal movement occurring. Several cases are calculated to verify the accuracy of torque estimation. Also, the influences factors are discussed in torque estimation considering CE. The results show that the proposed torque estimation method is demonstrated to have a higher accuracy compared with the traditional torque estimation. It is up to 50% of the maximum relative error between the torque with and without considering CE, which indicates the necessity to consider the CE into torque estimation for disc-type MR devices. And, it shows that the influence of CE could be reduced by decreasing MRF velocity and increasing yield stress in the design of MR devices.