Adaptive force tracking control of electrohydraulic systems with low load using the modified LuGre friction model

The force tracking performance of controllers is seriously degraded by the complex friction behaviors when the electrohydraulic system applies low load. The existing LuGre model is employed in the motion control system with the known trajectory. In this work, a modified LuGre model combined with a zero-velocity crossing window is established to address the lag issue and model oscillation in force control system. Then, the Stribeck curve in the friction model is accurately obtained using a fast measurement method, and the impact of friction parameters on the accuracy of the LuGre model is analyzed. Next, an adaptive friction compensation control scheme is proposed for the electrohydraulic system with low load using the modified LuGre model to compensate for dynamic friction behavior and improve the force tracking performance. The uncertain friction parameters are tuned online to reduce the force error of the low-velocity region via the derived adaptive law and a dual-observer. The disturbance observer is effectively integrated to reduce the negative influence of unconsidered dynamics. Finally, comparative experiments are conducted to verify the effectiveness of the proposed controller in static and dynamic loading modes.

Automated summary

This paper proposes a modified LuGre model and an adaptive friction compensation control scheme to address the complex friction behaviors and improve the force tracking performance of controllers in electrohydraulic systems with low load. The effectiveness of the proposed controller is verified through comparative experiments in static and dynamic loading modes.