Abstract
Brake judder investigation requires the understanding of the vibration transmission paths that
define how the vibration energy generated by the fluctuating brake torque is transmitted to the
vehicle body through the suspension parts and the chassis. This knowledge allows a more
accurate characterisation of brake judder problems in vehicles and it is a general tool to identify countermeasures for reducing the vehicle body and chassis sensitivity to brake judder
excitation.
Judder Transfer Path Analysis (JPA) is an analysis tool that allows us to assess the possible
ways of energy transfer from the brake to a given target location in a vehicle. It supplies the
tools required to locate the most important energy transfer paths for a specific problem, and to
evaluate their individual effects on the target, thus providing valuable insight into the
mechanisms responsible for the problem.
The essential elements in the analysis of this type of problem are:
· The excitation sources: structure and/or airborne, acoustical or vibration. Typical
sources include the vibration of a car engine, road induced vibrations or suspension
loads generated during brake judder.
· The target locations: These are typically acoustical or vibration perceived by the driver
in a car during operational conditions. In our case we focus on the vibration perceived
by a driver during the occurrence of brake judder. The target points to assess the vehicle
performance in these circumstances normally are the brake pedal, the steering wheel
and the seat rail [1] [2] [3].
· The structural transfer paths which are represented by the physical mounts and/or rigid
connections whereby the noise and vibration are transferred from the source to the
target location. In our case, this transfer paths will be structural paths that transmit the
suspension vibration excitation into the chassis and body hard-points when the brake
exhibits judder
KEYWORDS Judder, Path analysis, Chassis design, Brake testing, Vibrations