Investigation on Magnetorheological Brake Light Possible Application of for Rail Vehicle
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Date
2015-05
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Addis Ababa University
Abstract
Conventional pneumatic brake systems used in light rail vehicle have several limitations and
disadvantages such as the response delay in building up the pressure necessary to actuate the
brakes there is also, the long time delay between front and rear car, wear of braking pad and
requirement for auxiliary components (e.g. compressor, transfer pipes, auxiliary reservoir and
main reservoir) increase the overall weight and it is bulky in size of braking system. This
paper presents an electromechanical brake system for light rail vehicle using
magnetorheological (MR) fluid.
The proposed MR brake consists of rotating disks immersed into an MR fluid and an
enclosed electromagnet. When current is applied to the electromagnet coil, the MR fluid
solidifies as its yield stress varies as a function of the magnetic field applied by the
electromagnet. This controllable yield stress produces shear friction on the rotating disks,
generating a retarding braking torque. This type of braking system has the following
advantages: faster response, easy implementation of a new controller or existing controllers
(e.g. ABS etc.), less maintenance requirements since there is no material wear and lighter
overall weight since it does not require the auxiliary components.
In this paper practical design criteria such as material selection and MR fluid selection are
considered to select a basic MR brake configuration. The mechanical part is modeled using
Bingham’s equation, an approach to modeling the magnetic circuit is also proposed in this
work. The equation of the torque transmitted by the MR fluid within the brake is derived,
based on this equation, after mathematical manipulation, the torque generating by the MRB is
investigated theoretically. The MRB in a rail vehicle was studied using a 1/8th vehicle model.
Then, a finite element analysis is performed to investigate the resulting structural and heat
distribution within the MR brake configuration.
Results shows that MRB generates much lower braking torque compared to that of braking
torque required for train to stop and a finite element analysis results shows operating
temperature can intermittently reach outside the recommended temperature range of the MR
fluid, however possible design improvements are suggested to further increase the braking
torque capacity and to reduce temperature rise.
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Keywords
Magnetorheological Brake, Brake Light, Rail Vehicle, Investigation