Vol.1, No 9, 2002 pp. 1217 - 1230
UDC 681.513.3
POSITION CONTROL OF AN ELECTRO-HYDRAULIC
SERVO SYSTEM USING SLIDING MODE CONTROL
ENHANCED BY FUZZY PI CONTROLLER
Miroslav Mihajlov1, Vlastimir Nikolić1, Dragan Antić2
1 Department of Precise Mechanical Engineering and Automatic Control, University of Niš,
Faculty of Mechanical Engineering, Beogradska 14, 18000 Niš, Serbia and Montenegro
2 Department of Automatic Control, University of Niš,
Faculty of Electronic Engineering, Beogradska 14, 18000 Niš, Serbia and Montenegro
Abstract. Variable structure control with sliding mode, also called sliding mode control, is a particularly suitable as possible control solution in electro-hydraulic systems. In this paper, we apply the technique of the sliding mode control enhanced by fuzzy PI controller to a typical electro-hydraulic system, whose mathematical model accounts for the main nonlinearities including internal friction. The position control problem in the presence of unmodeled dynamics, parametric uncertainties and external disturbances was investigated. Fuzzy controller is added in the feedforward branch of the closed loop to improve the performance of the variable structure controller (with fixed boundary layer) with regard to the position precision and disturbance rejection. The performance improvement  is demonstrated through simulation results.
UPRAVLJANJE POZICIJOM ELEKTROHIDRAULIČKOG SISTEMA PRIMENOM REGULATORA PROMENLJIVE STRUKTURE PROŠIRENOG FAZI PI REGULATOROM
U ovom radu je primenjen regulator promenljive strukture proširen fazi PI regulatorom na tipični elektrohidraulički sistem čiji matematički model obuhvata glavne nelinearnosti, uklučujući trenje u hidrauličkom cilindru. Razmatran je problem upravljanja pozicijom u prisustvu nemodelirane dinamike, parametarskih neodređenosti i spoljašnjih poremećaja. Uvođenjem fazi regulatora u direktnu granu zatvorenog kola poboljšane su performanse sistema upravljanja promenljive strukture sa fiksnim graničnim slojem u odnosu na tačnost praćenja zadate trajektorije i eliminaciju spoljašnjeg poremećaja. Poboljšanje performansi je ilustrovano rezultatima simulacije.