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

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

Novel Adaptive Extended State Observer for Dynamic Parameter Identification with Asymptotic Convergence

In this paper, a novel method of parameter identification of linear in parameter dynamic systems is presented. The proposed scheme employs an Extended State Observer to online estimate a state of the plant and momentary value of total disturbance present in the system. A notion is made that for properly redefined dynamics of the system, this estimate can be interpreted as a measure of modeling error caused by the parameter uncertainty. Under this notion, a disturbance estimate is used as a basis for classic gradient identification. A global convergence of both state and parameter estimates to their true values is proved using the Lyapunov approach under an assumption of a persistent excitation. Finally, results of simulation and experiments are presented to support the theoretical analysis. The experiments were conducted using a compliant manipulator joint and obtained results show the usefulness of the proposed method in drive control systems and robotics

Architektura Systemu do zadań Rozwoju i Nadzoru Zrobotyzowanego Teleskopu Astronomicznego

In this paper the novel control and communication scheme designed to ease the development and maintenance of the robotic astronomical telescope device is presented. The proposed solution allows the user to remotely access any signal in the controller of the telescope without imposing any additional overhead during telescope operation. The implemented scheme can be used by both an automated control system and human operators for easy supervision, control, and maintenance of the device.Artykuł przedstawia nowy system sterowania i komunikacji zaprojektowany w celu usprawnienia rozwoju i utrzymania zrobotyzowanego montażu teleskopu astronomicznego. Proponowane rozwiązanie umożliwia użytkownikowi zdalny dostęp do dowolnych sygnałów wewnątrz sterownika bez zwiększonego obciążenia podczas pracy systemu. Zaimplementowane rozwiązanie może być wykorzystywane zarówno przez automatyczny system nadzorujący, jak i przez użytkownika lub operatora, do nadzoru, sterowania i utrzymania urządzenia

Analysis of an Impact of Inertia Parameter in Active Disturbance Rejection Control Structures

This paper is focused on a distributed control of fully actuated manipulators under operating conditions when dynamic couplings between their joints are insignificant. The main research aspect was to examine the influence of the inertia parameter on the tracking quality for control systems based on the active rejection paradigm. The theoretical description and preliminary hypothesis were supported by extensive simulation and experimental results. In particular, it is demonstrated that choosing the inertia parameter according to the real dynamics properties does not guarantee the best performance of the considered control structures

Effect of Co-Inoculation with <i>Saccharomyces cerevisiae</i> and Lactic Acid Bacteria on the Content of Propan-2-ol, Acetaldehyde and Weak Acids in Fermented Distillery Mashes

The qualitative and quantitative composition of volatile compounds in fermented distillery mash determines the quality of the obtained distillate of agricultural origin (i.e., raw spirit) and the effectiveness of further purification steps. Propan-2-ol (syn. isopropyl alcohol), due to its low boiling point, is difficult to remove by rectification. Therefore, its synthesis needs to be limited during fermentation by Saccharomyces cerevisiae yeast, while at the same time controlling the levels of acetaldehyde and acetic acid, which are likewise known to determine the quality of raw spirit. Lactic acid bacteria (LAB) are a common but undesirable contaminant in distillery mashes. They are responsible for the production of undesirable compounds, which can affect synthesis of propan-2-ol. Some bacteria strains are able to synthesize isopropyl alcohol. This study therefore set out to investigate whether LAB with S. cerevisiae yeast are responsible for conversion of acetone to propan-2-ol, as well as the effects of the amount of LAB inoculum and fermentation parameters (pH and temperature) on the content of isopropyl alcohol, acetaldehyde, lactic acid and acetic acid in fermented mashes. The results of NMR and comprehensive two-dimensional gas chromatography coupled with time of flight mass spectrometry (GC &#215; GC-TOF MS) analysis confirmed the ability of the yeast and LAB strains to metabolize acetone via its reduction to isopropyl alcohol. Efficient fermentation of distillery mashes was observed in all tested mashes with an initial LAB count of 3.34&#8211;6.34 log cfu/mL, which had no significant effect on the ethanol content. However, changes were observed in the contents of by-products. Lowering the initial pH of the mashes to 4.5, without and with LAB (3.34&#8211;4.34 log cfu/mL), resulted in a decrease in propan-2-ol and a concomitant increase in acetaldehyde content, while a higher pH (5.0 and 5.5) increased the content of propan-2-ol and decreased acetaldehyde content. Higher temperature (35 &#176;C) promoted propan-2-ol synthesis and also resulted in increased acetic acid content in the fermented mashes compared to the controls. Moreover, the acetic acid content rose with increases in the initial pH and the initial LAB count