This paper focuses on the use of the techniques based on linear matrix inequalities for robust H(infinity) position control synthesis of an electro-hydraulic servo system. A nonlinear dynamic model of the hydraulic cylindrical actuator with a proportional valve has been developed. For the purpose of the feedback control an uncertain linearized mathematical model of the system has been derived. The structured (parametric) perturbations in the electro-hydraulic coefficients are taken into account. H(infinity) controller extended with an integral action is proposed. To estimate internal states of the electro-hydraulic servo system an observer is designed. Developed control algorithms have been tested experimentally in the laboratory model of an electro-hydraulic servo system.
"The second, third and seventh lines from (10) are non-linear and need to be linearised for the purpose of controller design. It is typical in the literature to use expansion in the Taylor's series for linearisation as in , or to use a simplified analysis on the basis of the laws of physics yielding a linear set of equations as in . It is necessary to note that the derived non-linear model exhibits a switching behaviour as the spool position x 1 changes sign. "
[Show abstract][Hide abstract] ABSTRACT: The electro-hydraulic servo system (EHSS) demonstrates a relatively low level of efficiency compared to other available actuation methods. The objective of this paper is to increase this efficiency by introducing a variable supply pressure into the system and controlling this pressure during the task of position tracking. For this purpose, an EHSS structure with controllable supply pressure is proposed and its dynamic model is derived from the basic laws of physics. A switching control structure is then proposed to control both the supply pressure and the cylinder position at the same time, in a way that reduces the overall energy consumption of the system. The stability of the proposed switching control system is guaranteed by proof, and its performance is verified by experimental testing.
ISA Transactions 07/2014; 53(4). DOI:10.1016/j.isatra.2014.04.010 · 2.98 Impact Factor
"The objective of H 1 control is to design controllers such that the closed-loop system is internally stable and its H 1 norm from the external input to the controlled output is less than a prescribed level. Since the theory of H 1 control has proposed by Zames , much effort has been made in H 1 controller design in order to guarantee desired stability        . "
[Show abstract][Hide abstract] ABSTRACT: This paper investigates the observer-based H(∞) control problem for a class of discrete-time mixed delay systems with random communication packet losses and stochastic nonlinearities. The mixed delays comprise both discrete time-varying and distributed delays, the random data losses are described by a Bernoulli distributed white sequence that obeys a conditional probability distribution, and the stochastic nonlinearities in the form of statistical means cover several well-studied nonlinear functions. In the presence of mixed delays, random packet losses and stochastic nonlinearities, sufficient conditions for the existence of an observer-based feedback controller are derived, such that the closed-loop control system is asymptotically mean-square stable and preserves a guaranteed H(∞) performance.
ISA Transactions 11/2012; 52(2). DOI:10.1016/j.isatra.2012.10.001 · 2.98 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In order to solve the uncertainties in the position servo system, caused by servo system without modeling accurately, which may cause the deterioration of the control quality of the electro-hydraulic position servo system (EHPSS) and even lead to its instability, a dynamic sliding mode control strategy is proposed for an EHPSS. Based on dynamic switching function, the proposed control strategy has fast response and good disturbance rejection capability. The numerical simulation is presented to verify the effectiveness of the proposed control scheme. It is shown from the experimental results that the proposed controller offers several advantages such as fast response, good disturbance rejection capability, good position tracking capability and so forth. It is also revealed from simulation results that the proposed control strategy is valid for the EHPSS.
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