Dynamic analysis of planar multi body systems with LuGre friction at differently located revolute clearance joints
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.