Abstract: To address the impact and chattering problem when huge elastic load is running at a low speed, a load torque based variable universe double fuzzy control method is proposed. Consider the hydraulic servo system, a load force is used to solve the impact problem when the system is changing its’ velocity direction. Since the load force will change along with the displacement and the spring stiffness, a variable universe double fuzzy control scheme is proposed. Load force is applied to form the first fuzzy controller, which is aim to change the universe stretch and retraction factor. Traditional fuzzy proportion, integration, differentiation(PID) is used to adjust the PID parameter according to the feedback errors. A more suitable elastic load controller is then formed by combining these two fuzzy controllers. Simulations and experiments show that the proposed controller has the ability to address the impact and chattering problem with respect to huge elastic load while a better performance is maintained.

Key words: huge elastic load;hydraulic servo system;variable universe;double fuzzy controller