Tracking control for a cascade perturbed control system using the active disturbance rejection paradigm

In this paper the stability of a closed-loop cascade control system in the trajectory tracking task is addressed. The considered plant consists of underlying second-order fully actuated perturbed dynamics and the first order system which describes dynamics of the input. The main theoretical result presented in the paper concerns stability conditions formulated based on the Lyapunov analysis for the cascade control structure taking advantage of the active rejection disturbance approach. In particular, limitations imposed on a feasible set of an observer bandwidth are discussed. In order to illustrate characteristics of the closed-loop control system simulation results are presented. Furthermore, the controller is verified experimentally using a two-axis telescope mount. The obtained results confirm that the considered control strategy can be efficiently applied for mechanical systems when a high tracking precision is required.Comment: 17 pages, 8 figures, 2 table

Changes in the Chemical Composition of Plum Distillate During Maturation with Oak Chips under Different Conditions

U radu je ispitan utjecaj dozrijevanja u kontaktu s hrastovim trijeskama na sastav i koncentraciju destilata šljive. Destilatu šljive su tijekom starenja dodane lagano pržene trijeske francuskog hrasta (Quercus sessiflora i Quercus robur) ili trijeske dobivene od starih bačava u kojima je odležao konjak. Ispitan je utjecaj količine dodanih trijeski, temperature, načina dozrijevanja (statičnog ili uz cirkulaciju) te primjene ultrazvuka. Dozrijevanjem destilata šljive u prisutnosti hrastovih trijeski povećala se količina ekstraktibilnih organskih spojeva (uključujući tanine) i promijenila boja destilata, u ovisnosti o vrsti i količini dodanih trijeski te uvjetima dozrijevanja. Koncentracija se šećera, kao što su glukoza, ksiloza i arabinoza, povećala ovisno o uvjetima dozrijevanja i vrsti trijeski. Razgradnjom lignina oslobođene su određene količine sinapaldehida, siringaldehida, coniferaldehida i vanilina, u ovisnosti o uvjetima pokusa. Od hlapljivih spojeva, koncentracija se viših alkohola i alifatskih (acikiličkih) aldehida u većem broju varijanti pokusa smanjila, dok se koncentracija furanskih aldehida, ovisno o vrsti i količini trijeski te uvjetima dozrijevanja, povećala. Koncentracija se estera, poput etilacetata u većem broju varijanti pokusa smanjila, a etil-kaproata, etil-kaprilata i etil- -kaprata postupno povećala. Neki su fenoli i laktoni pronađeni u uzorcima destilata nakon dozrijevanja, a najmanje su koncentracije tih spojeva pronađene u uzorcima destilata dozrelog u kontaktu s hrastovim trijeskama dobivenim od bačava u kojima je odležao konjak.This study investigates the effect of ageing on the qualitative and quantitative composition of plum distillate in contact with oak wood chips. Maturation was performed with lightly toasted French oak (Quercus sessiflora and Quercus robur) chips or oak chips made from fragments of empty barrels that had been used for ageing cognac. The effects of oak chip dose, process temperature, ageing system (static or circulatory) and ultrasound treatment were assessed. Maturation of plum distillate samples with oak chips resulted in higher levels of extractable organics (including tannins) and colour changes, which were correlated with the type and dose of oak chips, and the conditions of maturation. The content of sugars such as glucose, xylose and arabinose also increased, depending on the conditions and type of oak chips. Degradation of lignin resulted in liberation of sinapaldehyde, syringaldehyde, coniferaldehyde and vanillin, with intensities depending on the applied parameters. In terms of volatiles, decreases in the concentration of higher alcohols and aliphatic aldehydes were observed in the majority of maturation experiments, while concentrations of furanic aldehydes increased depending on the type and dose of oak chips, as well as on the conditions of maturation. The quantities of esters such as ethyl acetate decreased in the majority of experimental variants, whereas concentrations of ethyl caproate, ethyl caprylate and ethyl caprate increased gradually. Some phenols and lactones were detected in all matured samples, with the lowest levels found in the samples aged with oak chips made from cognac barrels

Improving the Active Disturbance Rejection Controller Tracking Quality by the Input-Gain Underestimation for a Second-Order Plant

In this paper, a problem of influence of an input-gain uncertainty on the tracking performance of a control structure designed according to the Active Disturbance Rejection Control (ADRC) paradigm is investigated. This problem is exemplified using the second-order plant. It is presented that conscious choice of the input-gain parameter different to that of the real plant may lead to a significant improvement of the control precision if the controller is designed in an error domain. Obtained results indicate that the closed-loop system remains stable, and the tracking errors decrease if the value of this parameter follows from multiplying the plant gain input by a positive factor smaller than a certain threshold value. The upper limit for this factor is investigated in the paper and outcomes are presented for various implementation variants. Results of numerical computations, simulations and experiments are presented to consider this bounding value in individual cases