Variable Structure Systems: Survey

Coordinated Science Laboratory was formerly known as Control Systems Laborator

Technology of 3D Simulation of High-Speed Damping Processes in the Hydraulic Brake Device

This chapter describes a three-dimensional simulation technology for physical processes in concentric hydraulic brakes with a throttling-groove partly filled hydraulic cylinder. The technology is based on the numerical solution of a system of Navier–Stokes equations. Free surface tracking is provided by the volume of fluid (VOF) method. Recoiling parts are simulated by means of moving transformable grids. Numerical solution of the equations is based on the finite-volume discretization on an unstructured grid. Our technology enables simulations of the whole working cycle of the hydraulic brake. Results of hydraulic brake simulations in the counter-recoil regime are reported. The results of the simulations are compared with experimental data obtained on JSC “KBP” test benches. The calculated and the experimental sets of data are compared based on the piston velocity as a function of distance. The performance of the hydraulic brake is studied as a function of the fluid mass and firing elevation of the gun

Two sliding mode control approaches for the stator voltage amplitude regulation of a stand-alone WRSM

In this paper two sliding mode control alternatives to regulate the stator voltage amplitude for a stand alone wound rotor synchronous generator are presented. Both controllers use the stator voltage d-component error in the sliding surface. In a first case an outer PI loop controller is added to provide the proper d-voltage component reference. The second approach consists in extending the dynamic system to include the integral term as state variable and to modify the former sliding surface by adding this new state. Finally, simulations results are done in order to validate the proposed algorithms.Peer ReviewedPostprint (published version

Konturni regulator za precizne slijedne sustave

This paper discusses the trajectory generation algorithm, contour error construction method and finally the contour controller design. In the trajectory generation algorithm combination of elliptical Fourier descriptors (EFD) and time based spline approximation (TBSA) is used to generate position, velocity and acceleration references. Contour error is constructed using transformation of trajectory tracking errors. Transformation is computationally efficient and requires only reference velocity information. Contour controller is designed using sliding mode control. Experiments are performed on planar linear motion stage and significant contour error reduction is observed.U članku se raspravlja o algoritmu za generiranje trajektorija, metodi za konstrukciju pogreške konture te o sintezi konturnog regulatora. U algoritum za generiranje trajektorija, korištena je kombinacija eliptičnih Fourierovih odrednika (EFD) i vremenske aproksimacije splajnovima (TBSA) za odre.ivanje referentnih vrijednosti položaja, brzine i ubrzanja. Pogreška konture je konstruirana korištenjem transformirane pogreške slije.enja trajektorije. Transformacija je računski efikasna i potrebna joj je samo informacija o referentnoj brzini. Konturni regulator je projektiran koristeći upravljanje u kliznim režimima. Provedeni su eksperimenti na linearnom slijednom sustavu i primijećena su znatna smanjenja pogreške konture

Window observers for linear systems

<p>Given a linear system <math alttext="$dot x = Ax + Bu$"> <mrow> <mover accent="true"> <mi>x</mi> <mo>&dot;</mo> </mover> <mo>=</mo> <mi>A</mi> <mi>x</mi> <mo>+</mo> <mi>B</mi> <mi>u</mi> </mrow> </math> with output <math alttext="$y = Cx$"> <mrow> <mi>y</mi> <mo>=</mo> <mi>C</mi> <mi>x</mi> </mrow> </math> and a window function <math alttext="$omega left( t ight)$"> <mrow> <mi>&omega;</mi> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> </mrow> </math>, <emph>i.e</emph>., <math alttext="$forall t,omega left( t ight) in$"> <mrow> <mo>&forall;</mo> <mi>t</mi> <mo>,</mo> <mi>&omega;</mi> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>&isin;</mo> </mrow> </math> {0,1 }, and assuming that the window function is Lebesgue measurable, we refer to the following observer, <math alttext="$hat x = Ax + Bu + omega left( t ight)LC(x - hat x)$"> <mrow> <mover accent="true"> <mi>x</mi> <mo>&circ;</mo> </mover> <mo>=</mo> <mi>A</mi> <mi>x</mi> <mo>+</mo> <mi>B</mi> <mi>u</mi> <mo>+</mo> <mi>&omega;</mi> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <mi>L</mi> <mi>C</mi> <mo stretchy="false">(</mo> <mi>x</mi> <mo>&minus;</mo> <mover accent="true"> <mi>x</mi> <mo>&circ;</mo> </mover> <mo stretchy="false">)</mo> </mrow> </math> as a window observer. The stability issue is treated in this paper. It is proven that for linear time-invariant systems, the window observer can be stabilized by an appropriate design under a very mild condition on the window functions, albeit for linear time-varying system, some regularity of the window functions is required to achieve observer designs with the asymptotic stability. The corresponding design methods are developed. An example is included to illustrate the possible applications</p

Adaptive Simulation and Control of Variable-Structure Control Systems in Sliding Regimes

Conventional simulation and control methods for sliding mode control systems are limited by the available sampling bandwidth and allowable tracking error. Consequently, these methods suffer from harmful chattering. This paper presents an adaptive method for the discrete-time simulation and control of sliding mode control systems, based on an analysis on the relationship between tracking error and sampling rate for these systems. Our analysis shows that the tracking error decreases as the sampling time interval decreases when the sliding condition exists. The adaptive method exploits the concept of discrete-time sliding mode; the method adjusts its sampling rate to ensure that the tracking error is bounded within a boundary layer of the sliding surface. To simulate a sliding mode system in discrete time, we present an adaptive integration scheme that follows the ideal system within a given tolerance. Likewise, the adaptive method can be used to generate discrete control signals for sli..