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Semi-actively controlled magnetorheological damper of electric motor fork
Blahuta, Jiří ; Vimmr, Jan (referee) ; Kubík, Michal (advisor)
The passive dampers used today, which work by dissipating energy using an oil fill, allow only limited damping force adjustment, which must be set before driving. Passive dampers are at their peak in terms of design and no further advances in ride comfort are expected. This is where magnetorheological dampers have the potential to increase ride comfort and improve handling with semi-active control. They achieve better performance thanks to a rapid change in damping force, which can then be controlled almost instantly according to the current driving conditions. MR dampers are already successfully used in the automotive sector but have not yet made a commercial breakthrough in the cycling segment. The main reason is their high weight compared to current passive dampers. The aim of this work is to design a lightweight and fast MR damper for the fork of a Kuberg electric motorbike. For the success of the product, the weight of the design needs to be minimized. For the proper operation of a semi-active damper, it is necessary to achieve a fast time response of the damping force, which is most affected by the occurrence of eddy currents in the magnetic circuit. Another problem is to achieve sufficient damping force in the activated state, so a suitable prediction model must be used. The design of the damper also needs to be able to fit into the limited space of the fork and the damper must be fitted with sensors. The result of this work is the design of two generations of MR damper and the fabricated working sample. Generation I MR damper was used for testing and verification of the model. Generation II MR damper is then the final design with reduced mass. The weight of the generation II damper is only 19% higher than the original passive damper. The total weight of the MR damper is 1,6 kg. The new MR damper retains the original dimensions and stroke and has integrated sensors in the design. The proposed MR damper has the potential to be successful in the electric bicycle segment and other electric single-track vehicles where its implementation is most advantageous. However, it can also be used in conventional mountain bikes. Together with a semi-active control unit, it allows for better ride comfort and handling characteristics.
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