Precise position control of an electro-hydraulic servo system via robust linear approximation.

Area of Science:

• Control Systems Engineering
• Nonlinear Dynamics
• Robotics

Background:

• Electro-hydraulic servo systems (EHSS) exhibit significant nonlinearity, complicating accurate modeling for control.
• Linearization of nonlinear systems, while common, introduces uncertainties that can degrade control performance.

Purpose of the Study:

• To develop a robust linearization method for electro-hydraulic servo systems (EHSS) for position control.
• To synthesize an output-feedback H∞ controller using the derived linear model.
• To reduce conservatism and improve the accuracy of the linearized system model.

Main Methods:

• Investigated multiple linearization uncertainty methods, including bound-based and graphical polytope extraction.
• Proposed a novel, less conservative procedure for extracting linear models from nonlinear EHSS.
• Employed Linear Matrix Inequality (LMI) techniques for synthesizing an output-feedback H∞ controller.

Main Results:

• The proposed linearization procedure effectively reduces model uncertainty and conservativeness.
• The synthesized H∞ controller demonstrated optimal performance in simulations and experiments.
• The system achieved fast position control without any overshoot, validating the method's efficacy.

Conclusions:

• The novel linearization technique provides a more accurate and less conservative model for electro-hydraulic servo systems.
• The LMI-based H∞ controller design ensures robust and efficient position control.
• The study successfully bridges the gap between nonlinear system complexity and linear control design for EHSS.