Magnetorheological (MR) dampers have been widely investigated and proposed for vibration mitigation systems because they possess continuous variability of damping coefficient in response to different operating conditions. In the conventional design of MR dampers, a separate controller and power supply are required, causing an increment of complexity and cost, which are not suitable for home appliances like washing machines. To solve these issues and to reuse wasted energy from vibration of washing machines, in this study, a self-powered shear-mode MR damper, which integrates MR damping and energy-harvesting technologies into a single device, is proposed. The MR damper is composed of an inner housing, on which magnetic coils are wound directly, and an outer housing for covering and creating a closed magnetic circuit of the damper. The gap between the inner housing and the moving shaft is filled with MR fluid to produce the damping force. The energy-harvesting part consists of permanent magnets fastened together on the shaft and induction coils wound directly on slots of the housing. The induced power from the induction coils is directly applied to the excitation coils of the damping part to generate a corresponding damping force against the vibration. In order to achieve optimal geometry of the self-powered MR damper, an optimization for both the damping part and the energy harvesting part of the proposed dampers are conducted based on ANSYS finite element analysis. From optimal solutions, a prototype of the proposed damper is designed in detail, manufactured, and experimentally validated.

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This paper deals with a novel self-adaptive magneto-rheological (MR) damper in shear-mode which can control vibrations of washing machines more effectively than commercial passive dampers. The damper comprises a shaft and a housing sliding relatively on a gap filled with MR fluid (MRF). Permanent magnets are fastened on the two shaft ends leaving a middle plain shaft part. The greater the vibration the more magnets enter the MRF region, which results in a higher damping force to attenuate the vibration. Compared with conventional and self-powered MR dampers, the proposed damper has much lower cost for commercial ability since it can itself adjust damping levels corresponding to external vibratory excitations without any control equipment or power unit. It also has simple and compact structure (no magnetic coils), which facilitate manufacturing and maintenance. Another remarkableness of the proposed MR damper is its displacement-dependent damping characteristic which extremely conforms to operation of washing machines. After an overview of the state of the art of vibration control for washing machines, the proposed self-adaptive MR damper is configured. Major geometry of the proposed damper is then optimized to satisfy production cost, size, installation space, off-state force and desired damping force. Based on the obtained optimal solutions, detailed design of the damper is performed and two damper prototypes are manufactured. The dampers are then installed in a prototype washing machine for testing and their experimental performances are compared with conventional passive dampers.