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Modelling of a combined system of hydraulic magnetorheological fluid damper with braking-by-wire system
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
A hydraulic chamber is embedded in serial with the accumulator of a normal mono-tube magnetorheological fluid damper (MRFD). The damper stiffness can be adjusted by changing the initial accumulator volume with the hydraulic chamber. This hydraulic chamber is connected to an electric pump and controlled by the braking-by-wire system. Some signals and control parameters of the braking system are shared with the suspension system. A modified bi-viscosity magnetorheological fluid (MRF) model that explicitly includes the parameter of control current is adopted to determine the viscous forces of the damper. A dynamic model of this hydraulic MRFD is subsequently set up based on the hydro dynamic system and the MRF model. In this scheme, both the MRF viscosity and the damper stiffness can be continuously adjusted at the same time. A theoretical model combining the vehicle dynamics, the braking-by-wire system and the hydraulic MRFD is established based on which the control principles of the hydraulic MRFD according to the braking intensity are revealed. Simulations are carried out to study the parametric influences of this combined braking and suspension system on the vehicle stance in emergency braking. Results show that the hydraulic chamber provides rapid variation of the external force through nonlinear distortion of the external performances that is caused by accumulator volume variations. In the case of emergency braking, the coupled effects of the braking system and the hydraulic MRFD can effectively resist the vehicle pitch motion and enhance the vehicle body stability. With different braking intensity, the effects of the hydraulic MRFD on the vehicle stance are studied and compared with that of the normal MRFD. It shows that in the same conditions, the hydraulic MRFD can keep the vehicle stance in much wider range than the normal MRFD.