We developed a mathematical model of an unstable system of set of N connected inverted pendula. We described principles of stabilization of such a system at the neighborhood of the unstable upright ...position. Also, we studied dynamics of this system and obtained the limiting conditions ensuring the stability of this system. Simulation results demonstrate several important features of the system's dynamics.
This article studies the problem of prescribed-time global stabilization of a class of nonlinear systems, where the nonlinear functions are unknown but satisfy a linear growth condition. By using ...solutions to a class of parametric Lyapunov equations containing a time-varying parameter that goes to infinity as the time approaches the prescribed settling time, linear time-varying feedback is designed explicitly to solve the considered problem, with the help of a Lyapunov-like function. It is shown moreover that the control signal is uniformly bounded by a constant depending on the initial condition. Both linear state feedback and linear observer-based output feedback are considered. The effectiveness of the proposed approach is illustrated by a numerical example borrowed from the literature.
Time-varying features are generally considered to be detrimental to the analysis and design of control systems. This paper establishes methods to design bounded linear time-varying (LTV) controllers ...such that the control performance of a linear time-invariant (LTI) system can be improved, that is, the finite-time stability of the closed-loop system can be obtained. Specifically, for an LTI control system, by using the solution to a parametric Lyapunov equation (PLE), a bounded LTV controller containing a suitable time-varying parameter is designed. By fully exploiting properties of the solution to the PLE, it is shown that the closed-loop system is finite-time stable. Both state feedback and observer based output feedback, in which both the observer gain and the state feedback gain are time-varying, are considered. As a consequence, the finite-time semi-global stabilization and the fixed-time (prescribed finite-time) stabilization problems for linear systems by bounded controls are solved. The established method is utilized to the design of the spacecraft rendezvous control system and its effectiveness is verified by simulations.
360° video stabilization Kopf, Johannes
ACM transactions on graphics,
11/2016, Letnik:
35, Številka:
6
Journal Article
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We present a hybrid 3D-2D algorithm for stabilizing 360° video using a deformable rotation motion model. Our algorithm uses 3D analysis to estimate the rotation between key frames that are ...appropriately spaced such that the right amount of motion has occurred to make that operation reliable. For the remaining frames, it uses 2D optimization to maximize the visual smoothness of feature point trajectories. A new low-dimensional flexible deformed rotation motion model enables handling small translational jitter, parallax, lens deformation, and rolling shutter wobble. Our 3D-2D architecture achieves better robustness, speed, and smoothing ability than either pure 2D or 3D methods can provide. Stabilizing a video with our method takes less time than playing it at normal speed. The results are sufficiently smooth to be played back at high speed-up factors; for this purpose we present a simple 360° hyperlapse algorithm that remaps the video frame time stamps to balance the apparent camera velocity.
This work is concerned with the feedback stabilization of a class of semilinear system with distributed delay. We consider an observation condition in terms of the semigroup solution of the linear ...part of the considered system and parameterized by a positive constant. Some sufficient conditions are given with respect to this parameter and the bounded feedback control to guarantee the feedback stabilization of the semilinear system with distributed delay. Moreover, when this parameter is greater than or equal to 2, an explicit polynomial decay rate of the stabilization state is estimated in the strong stabilization case. In the bilinear case with distributed delay and by using the decomposition method of the state space, we investigate the feedback stabilization of the considered system using some suitable conditions like observability assumption. In the case of strong stabilization, we obtain the same explicit decay estimate of the stabilized state. Furthermore, when the parameter equal to 2, we show that the normalized feedback control exponentially stabilizes the semilinear system. The obtained results are illustrated by three examples and numerical simulations for wave equation with distributed delay.
A review on the immobilization of bromelain Tacias-Pascacio, Veymar G.; Castañeda-Valbuena, Daniel; Tavano, Olga ...
International journal of biological macromolecules,
July 2024, 2024-07-00, 20240701, Letnik:
273, Številka:
Pt 2
Journal Article
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This review shows the endeavors performed to prepare immobilized formulations of bromelain extract, usually from pineapple, and their use in diverse applications. This extract has a potent ...proteolytic component that is based on thiol proteases, which differ depending on the location on the fruit. Stem and fruit are the areas where higher activity is found. The edible origin of this enzyme is one of the features that determines the applications of the immobilized bromelain to a more significant degree. The enzyme has been immobilized on a wide diversity of supports via different strategies (covalent bonds, ion exchange), and also forming ex novo solids (nanoflowers, CLEAs, trapping in alginate beads, etc.). The use of preexisting nanoparticles as immobilization supports is relevant, as this facilitates one of the main applications of the immobilized enzyme, in therapeutic applications (as wound dressing and healing components, antibacterial or anticancer, mucus mobility control, etc.). A curiosity is the immobilization of this enzyme on spores of probiotic microorganisms via adsorption, in order to have a perfect in vivo compatibility. Other outstanding applications of the immobilized enzyme are in the stabilization of wine versus haze during storage, mainly when immobilized on chitosan. Curiously, the immobilized bromelain has been scarcely applied in the production of bioactive peptides.
This paper investigates the finite-time and fixed-time stabilization (FFTS) of switched systems with discontinuous dynamics, external disturbances and delays. Firstly, a new parameterized ...discontinuous stabilizer is designed to ensure the FFTS of switched discontinuous systems in the sense of Filippov solutions. Secondly, a detailed analysis is provided on how to regulate the power parameters to determine the settling time is finite or fixed. Thirdly, a new adaptive controller is further designed to stabilize the considered system in a finite time, and the corresponding settling time is estimated as well. Finally, two examples are given to demonstrate the efficiency of the proposed method.
The formation and stabilization of soil organic matter (SOM) are major concerns in the context of global change for carbon sequestration and soil health. It is presently believed that lignin is not ...selectively preserved in soil and that chemically labile compounds bonding to minerals comprise a large fraction of the SOM. Labile plant inputs have been suggested to be the main precursor of the mineral‐bonded SOM. Litter decomposition and SOM formation are expected to have temperature sensitivity varying with the lability of plant inputs. We tested this framework using dual 13C and 15N differentially labeled plant material to distinguish the metabolic and structural components within a single plant material. Big Bluestem (Andropogon gerardii) seedlings were grown in an enriched 13C and 15N environment and then prior to harvest, removed from the enriched environment and allowed to incorporate natural abundance 13C–CO2 and 15N fertilizer into the metabolic plant components. This enabled us to achieve a greater than one atom % difference in 13C between the metabolic and structural components within the plant litter. This differentially labeled litter was incubated in soil at 15 and 35 °C, for 386 days with CO2 measured throughout the incubation. After 14, 28, 147, and 386 days of incubation, the soil was subsequently fractionated. There was no difference in temperature sensitivity of the metabolic and structural components with regard to how much was respired or in the amount of litter biomass stabilized. Only the metabolic litter component was found in the sand, silt, or clay fraction while the structural component was exclusively found in the light fraction. These results support the stabilization framework that labile plant components are the main precursor of mineral‐associated organic matter.
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