Analysis of selected friction properties with the Froude pendulum as an example

- The b-spline curve use in the LuGre model ensures a full functionality of the model.
- The b-spline curve allows for complex shapes friction characteristics approximation.
- Froude pendulum allows for testing friction at low and high slip speed ranges.
- Kinetic friction coefficient should be determined while exposed to frictional lag.
- Clearance up to 0.1 mm has no significant effect on the pendulum trajectory motion.

The paper presents the method of friction parameters identification of the shaft-sleeve kinematic pair with the Froude pendulum as an example. Experimental and numerical tests covered the range of a small relative displacement of frictional pairs at which the hysteresis friction effects appear as well as the range of significant sliding velocities when the frictional force value results from the static relation to the friction coefficient characteristics. The pendulum motion description has involved a modified LuGre model, in which the Stribeck curve was replaced by cubic b-spline curve to enable the complex course approximation of friction coefficient characteristics. The specific behaviours of the pendulum motion observed during the experimental tests have been reproduced by simulating the modified LuGre model. Moreover, the numerical tests have demonstrated that the radial pendulum clearance up to 0.1 mm causes high-frequency oscillation, not substantially affecting the pendulum trajectory and sliding velocity.