The adaptive disturbance cancellation problem is considered for single-input, single-output, linear systems when the linear exosystem which generates the disturbances to be rejected and/or the ...reference signals to be tracked is unknown, that is both its order 2r+1 and its parameters {ω1,…,ωr} are unknown. The proposed regulator makes use of two observers and contains an adaptive internal model which tunes m internal parameters on the basis of the output regulation error. It is shown that: if m≥r, that is the adaptive internal model can reproduce the required input, the regulation error tends exponentially to zero; if m<r, that is the adaptive internal model can only approximate the required input within an approximation error ϵ, the regulation error tends exponentially into a closed ball whose radius is proportional to ϵ, provided that ϵ is sufficiently small so that singularities are avoided.
In order to more accurately model time-varying nonlinear systems, we propose a regularized online sequential extreme learning machine with adaptive regulation factor (ROSELM-ARF). The construction of ...a new objective function allows for the online updating of both the model coefficient as well as the regulation factor, while negating the influence of the cumulate error. This differs from the traditional regularized online sequential extreme learning machine (ReOS-ELM) which only updates the model coefficient. The development and application of a two-step solving method is used to determine the optimal parameters, where the optimal regulation factor is derived using the proposed fast and online leave-one-out cross validation (FOLOO) method. The computational performance could be drastically improved by using the proposed FOLOO method as compared to using the existing leave-one-out cross validation (LOO) method. The application of the proposed method in the modeling of two practical cases is done in order to demonstrate its effectiveness. The experimental results indicate that the proposed method provides a more accurate model than several conventional modeling methods, while also improving the computational performance.
Adaptive regulation is an important issue with a lot of potential for applications in active suspension, active vibration control, disc drives control and active noise control. One of the basic ...problems from the “control system” point of view is the rejection of multiple unknown and time varying narrow band disturbances without using an additional transducer for getting information upon the disturbances. An adaptive feedback approach has to be considered for this problem. Industry needs to know the state of the art in the field based on a solid experimental verification on a representative system using currently available technology. The paper presents a benchmark problem for suppression of multiple unknown and/or time-varying vibrations and an associated active vibration control system using an inertial actuator with which the experimental verifications have been done. The objective is to minimize the residual force by applying an appropriate control effort through the inertial actuator. The system does not use any additional transducer for getting real-time information about the disturbances.
The benchmark has three levels of difficulty and the associated control performance specifications are presented. A simulator of the system has been used by the various contributors to the benchmark to test their methodology. The procedure for real-time experiments is briefly described.11The GIPSA-LAB team has done the experiments for all the contributors. The performance measurement methods used will be presented as well as an extensive comparison of the results obtained by various approaches.22Simulation and Real-time results are presented by each contributor in their papers 3,11,17,30,10,1,7.
The SNAT2 (SLC38A2) System A amino acid transporter mediates Na
-coupled cellular uptake of small neutral α-amino acids (AAs) and is extensively regulated in response to humoral and nutritional cues. ...Understanding the basis of such regulation is important given that AA uptake
SNAT2 has been linked to activation of mTORC1; a major controller of many important cellular processes including, for example, mRNA translation, lipid synthesis, and autophagy and whose dysregulation has been implicated in the development of cancer and conditions such as obesity and type 2 diabetes. Extracellular AA withdrawal induces an adaptive upregulation of SNAT2 gene transcription and SNAT2 protein stability but, as yet, the sensing mechanism(s) that initiate this response remain poorly understood although interactions between SNAT2 and its substrates may play a vital role. Herein, we have explored how changes in substrate (AA and Na
) availability impact upon the adaptive regulation of SNAT2 in HeLa cells. We show that while AA deprivation induces SNAT2 gene expression, this induction was not apparent if extracellular Na
was removed during the AA withdrawal period. Furthermore, we show that the increase in SNAT2 protein stability associated with AA withdrawal is selectively repressed by provision of SNAT2 AA substrates (
-methylaminoisobutyric acid and glutamine), but not non-substrates. This stabilization and substrate-induced repression were critically dependent upon the cytoplasmic N-terminal tail of SNAT2 (containing lysyl residues which are putative targets of the ubiquitin-proteasome system), because "grafting" this tail onto SNAT5, a related SLC38 family member that does not exhibit adaptive regulation, confers substrate-induced changes in stability of the SNAT2-5 chimeric transporter. In contrast, expression of SNAT2 in which the N-terminal lysyl residues were mutated to alanine rendered the transporter stable and insensitive to substrate-induced changes in protein stability. Intriguingly, SNAT2 protein stability was dramatically reduced in the absence of extracellular Na
irrespective of whether substrate AAs were present or absent. Our findings indicate that the presence of extracellular Na
(and potentially its binding to SNAT2) may be crucial for not only sensing SNAT2 AA occupancy and consequently for initiating the adaptive response under AA insufficient conditions, but for enabling substrate-induced changes in SNAT2 protein stability.
A considerable amount of the thiamin generated by gut microbiota exists in the form of thiamin pyrophosphate (TPP). We have previously shown that human colonocytes possess an efficient ...carrier-mediated uptake process for TPP that involves the SLC44A4 system and this uptake process is adaptively regulated by prevailing extracellular TPP level. Little is known about the molecular mechanisms that mediate this adaptive regulation. We addressed this issue using human-derived colonic epithelial NCM460 cells and mouse colonoids as models. Maintaining NCM460 cells in the presence of a high level of TPP (1 mM) for short (2 days)- and long-term (9 days) periods was found to lead to a significant reduction in
H TPP uptake compared with cells maintained in its absence. Short-term exposure showed no changes in level of expression of SLC44A4 protein in total cell homogenate (although there was a decreased expression in the membrane fraction), mRNA, and promoter activity. However, a significant reduction in the level of expression of the SLC44A4 protein, mRNA, and promoter activity was observed upon long-term maintenance with the substrate. Similar changes in Slc44a4 mRNA expression were observed when mouse colonoids were maintained with TPP for short- and long-term periods. Expression of the transcription factors ELF3 and CREB-1 (which drive the SLC44A4 promoter) following long-term exposure was unchanged, but their binding affinity to the promoter was decreased and specific histone modifications were also observed. These studies demonstrate that, depending on the period of exposure, different mechanisms are involved in the adaptive regulation of colonic TPP uptake by extracellular substrate level.
In order to solve the problems of bottom pod leakage and soil removal by header, a soybean header profiling system was designed in this paper. The cutter height off-ground detection device was ...installed on both sides of the header, and the cutter distance from the ground was represented by the angle sensor turning when the profiling wheel met the rolling ground. The hydraulic electromagnetic reversing valve was installed so that the profiling system could automatically control the lifting of the header, the unilateral power of the solenoid valve was 0.15 s, and the height of the cutter from the ground was changed by 10 mm. The height of the cutter off the ground was set to 80 mm, and the adjustment range of the soybean header profiling system was 45–125 mm. The test results showed that the maximum absolute error of the cutter off the ground height detection device was 5.98 mm, the minimum absolute error was 1.00 mm, and the relative error was 0.038. The cutter height adjustment device was powered for 0.15 s, and the average adjustment distance was 11.158 mm. The soybean header profiling system did not shovel soil during field harvest, and the stubble height of 85% of soybean plants was less than 10 mm from the set height after harvest. The results showed that the soybean header profiling system could effectively adjust the cutter height from the ground so that the cutter height from the ground was kept at 80 mm. This study could provide a reference for the intelligent design of soybean harvesters.
The hemodynamic conditions and partial pressure of oxygen in microcirculation generally indicate the status of tissue perfusion, which provides essential information for the assessment and treatment ...of critical diseases such as sepsis. The human tongue is known to have abundant microcirculation and is an ideal window to observe the microcirculation. At present, the monitoring of sublingual microcirculation is mostly achieved using handheld vital microscopy (HVM). Microcirculation is organized and works as a network. However, HVM can obtain only limited view of few vessels and is not able to acquire information regarding the entire network. In this work, we proposed a method to construct a mathematical network model of sublingual microcirculation to solve the problems. The proposed method is based on fractal analysis to model and simulate the hemodynamic and functional activities of sublingual microcirculation. Specifically, the HVM technology is used to obtain the partial morphological and hemodynamic data of sublingual microcirculation, and fractal analysis is applied thereafter to establish the hemodynamic model of the network based on the data from few vessels. Further, the adaptive regulation mechanism of microcirculation is introduced to enhance the performance of the model. The model was validated by the experimental data and the results are consistent with the characteristics of microcirculation. The work demonstrates the potential of the proposed method in sublingual microcirculation research and for the further assessment of tissue perfusion.
•HVM) is not able to acquire information regarding the entire sublingual microvascular network.•Use the fractal technology to establish entire microvascular structure.•Use the adaptive regulation model to simulate the entire network's regulatory mechanism.•The experiment proved the above methods can be used to get entire network's hemodynamic and oxygen partial pressure information.
Mathematical models can produce desired dynamics and statistical properties with the insertion of suitable nonlinear terms, while energy characteristics are crucial for practical application because ...any hardware realizations of nonlinear systems are relative to energy flow. The involvement of memristive terms relative to memristors enables multistability and initial-dependent property in memristive systems. In this study, two kinds of memristors are used to couple a capacitor or an inductor, along with a nonlinear resistor, to build different neural circuits. The corresponding circuit equations are derived to develop two different types of memristive oscillators, which are further converted into two kinds of memristive maps after linear transformation. The Hamilton energy function for memristive oscillators is obtained by applying the Helmholz theorem or by mapping from the field energy of the memristive circuits. The Hamilton energy functions for both memristive maps are obtained by replacing the gains and discrete variables for the memristive oscillator with the corresponding parameters and variables. The two memristive maps have rich dynamic behaviors including coherence resonance under noisy excitation, and an adaptive growth law for parameters is presented to express the self-adaptive property of the memristive maps. A digital signal process (DSP) platform is used to verify these results. Our scheme will provide a theoretical basis and experimental guidance for oscillator-to-map transformation and discrete map-energy calculation.
This paper addresses the global output feedback regulation problem for a class of uncertain feedforward stochastic nonlinear systems. Unlike the previous works, the drift's growth rate depends not ...only on an unknown constant but also on an output polynomial function and an input function. Moreover, the diffusion's growth rate depends on an unknown constant or an output polynomial function and an input function. By using the general stochastic convergence theorem, an output controller is constructed to guarantee the boundedness and stochastic convergence of the resulting closed-loop system.
The paper considers the adaptive regulation for the Hammerstein and Wiener systems with event-triggered observations. The authors adopt a direct approach, i.e., without identifying the unknown ...parameters and functions within the systems, adaptive regulators are directly designed based on the event-triggered observations on the regulation errors. The adaptive regulators belong to the stochastic approximation algorithms and under moderate assumptions, the authors prove that the adaptive regulators are optimal for both the Hammerstein and Wiener systems in the sense that the squared regulation errors are asymptotically minimized. The authors also testify the theoretical results through simulation studies.
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