LuGre Friction Model: Application to a Pneumatic Actuated System

Pneumatic systems offer a wide range of load capacity and velocities, present advantageous power to weight ratios and do not generate thermal or magnetic fields. However, their broader use in industry has been hindered by the difficulties found in fine motion or force control. Amongst the several phenomena that contribute to this scenario, friction in piston and rod seals is probably the most important one. Industrial pneumatic cylinders present friction forces with several undesired features for control purposes like highly nonlinear behavior, hysteresis and dwell time dependence. The LuGre friction model presents a good trade-off between complexity and accuracy. In this work the LuGre model of an industrial pneumatic cylinder is identified and validated using experimental data. Static and dynamic parameters are estimated using a procedure described in literature and a new procedure to estimate one of the dynamic parameters is proposed. A comparison between both methods is provided.