Design and analysis of a new magneto rheological damper for washing machine

In this article, a new magneto rheological (MR) sponge damper is proposed for suppression of vibrations in a washing machine. The article presents design optimization of geometric parameters of MR sponge damper (MRSD) using the finite element analysis (FEA) and first order derivative techniques for a washing machine. The article explains the hysteresis behavior and the relationship of damping force with input current for the proposed MRSD. Moreover, the characteristics of the MRSD such as energy dissipation and equivalent damping coefficient are investigated experimentally in terms of input current and excitation amplitude. The passive dampers installed in washing machine are ineffective in reducing unwanted vibrations at resonant frequencies due to real time unbalanced mass. For this purpose, a test setup is established in order to compare the performance of passive dampers with the proposed MRSDs in a washing machine. It is noticed that MRSDs reduce average vibrations of 75.61 % in a low frequency band, whereas in a high frequency band, the MRSDs lessen average vibrations of 30.57 % in a washing machine. In order to determine the performance of proposed design MRSD, a detailed comparison of the performance parameters, such as total damping force, passive force, maximum average vibrations after suppression by MR dampers, maximum current and power ratings is provided with the existing designs of MR damper for washing machine from the literature.     

Active damping of chatter in the boring process via variable gain sliding mode control of a magnetorheological damper

In this article, a sliding mode control of a magnetorheological fluid damper is presented for active damping of chatter in the boring process for the first time. A boring bar is integrated with an in-house developed magnetorheological fluid damper system. The variable gain super twisting sliding mode control algorithm is designed and implemented for suppressing the chatter in the boring process. Simulations of the controller show its fast response and robustness against disturbances and parametric uncertainties. Validation cutting tests performed under various machining conditions showed that the stability limit can be increased significantly with the sliding mode control of the magnetorheological fluid damper.