Abstract:
In this paper, the dynamic response of a planar rigid multi-body system with
stick–slip friction in revolute clearance joints is studied. LuGre friction law is proposed to
model the stick–slip friction at the revolute clearance joints. This is because using this law,
one can capture the variation of the friction force with slip velocity, thus making it suitable
for studies involving stick–slip motions. The effective coefficient of friction is represented as
a function of the relative tangential velocity of the contacting bodies, that is, the journal and
the bearing, and an internal state. In LuGre friction model, the internal state is considered to
be the average bristle deflection of the contacting bodies. By applying the LuGre friction law
on a typical slider–crank mechanism, the friction force in the revolute joint having clearance
is seen not to have a discontinuity at zero slip velocity throughout the simulation unlike in
static friction models. In addition, LuGre model was observed to capture the Stribeck effect
which is a phenomenon associated directly with stick–slip friction. The friction forces are
seen to increase with increase in input speed. The effect of stick–slip friction on the overall
dynamic behavior of a mechanical system at different speeds was seen to vary from one
clearance joint to another.
