Adaptive compensation of dynamic friction in an industrial robot

A new dynamic model to describe joint friction in a industrial robot is presented. This model is an extension of the popular LuGre dynamic friction model. However, the description of the Stribeck effect is modeled with a first order nonlinear differential equation. This yields a second order dynamic friction model that still preserves the intuitive base of previous models, reproduces the pseudo-steady state behavior and offers the same input-output properties. The advantage with respect to other dynamic friction models is in the possibility of identifying all the relevant parameters. This particularly important when this parameters change with time making it difficult to continuously calibrate the model. The validity of a dynamic friction adaptive compensation scheme is verified by means of experimental results.