Elaborate Measuring System for Sensitivity Analyses and In-Depth Investigations of a Squealing Brake System

Brake squeal is an elusive problem which has been the subject of investigation for many decades, but there is still a lack of knowledge regarding the excitation mechanisms. New vehicle solutions, for instance the electrical vehicle, will have a lower general noise level. Thus, silent brake systems will gain in importance. To obtain such systems, in-depth investigations of the brake disc/pad contact are required.
For these investigations a new sensor has been developed. The guide pins of the caliper are replaced by modified ones which measure the friction force. Additionally, eddy current sensors are installed for contact-free measurement of the pad movement. Furthermore, triaxial acceleration sensors are mounted in the disc vents. Thus, it is possible to evaluate the operational deflection shapes of the disc.
Next, an extensive sensibility analysis is performed. Parameters such as environmental conditions, friction coefficient and many others are thereby changed. For example shown is the root mean square (RMS) value of the out-of-plane vibration of one acceleration sensor mounted in the brake disc vents. Five revolutions are depicted in the polar axis plot. The sensor passes the contact area at an angle of ± 18 degrees. The significant higher value at running-in occurs only when squealing is present.
The innovative design of the guide pin sensors allows measurements with a very high resolution. Thus, the friction force and even the superposed vibration of this force can be measured. The results lead to further insights regarding brake squeal triggering mechanisms.