A Newton-like algorithm for L2-gain optimal control of an electro-hydraulic servo-system

This paper is concerned with L₂-gain optimal control approach for rotary electro-hydraulic servo-system. The electro-hydraulic dynamics with respect to hydraulic motor velocity, with input voltage to the servo valve as control input and load torque as disturbance input, is formulated. The mathematical model results in input-affine nonlinear system. A numerical algorithm based on Newton method to solve a finite-horizon minimax problem for L₂-gain minimisation of electro-hydraulic system is presented. The feedback control and disturbance variables are formulated as linear combination of approximation functions. The proposed algorithm, which has recursive matrix structure, directly finds approximations of the feedback control and the “worst case” disturbance variables. Developed controller has been tested experimentally in the laboratory model of an electro-hydraulic servo system.