Friction force oscillations caused by changes in the properties of the contact zone between brake disc and pad are well known from various applications. Resulting effects like brake judder are known phenomena in brake technologies and in the scope of various scientific work. A new potential measure to reduce brake torque oscillations is the active compensation with the use of the control system of a self-energizing hydraulic brake (SEHB).
The SEHB for railway application developed at the Institute for Fluid Power Drives and Controls (IFAS) of RWTH Aachen University offers high dynamic properties with its capability to reduce brake torque oscillations actively. New — in comparison to other braking systems — is the fact that the brake torque is measured by sensing the pressure in an additional supporting cylinder. Within this paper the influence of the hydraulic-mechanical system of the supporting cylinder on the oscillation properties of the SEHB is analyzed. The experimental investigation is conducted using a full scale brake test for railway applications. The brake disc is driven by hydraulic motors in secondary control mode. Measurement results will be used to define requirements of a superimposed dynamic pressure control to minimize brake torque oscillations. Future work will be experimental investigation of the influence of the self-energizing effect and the development of measures to compensate brake torque oscillations actively with the hydraulic actuator of the SEHB.
