Adaptive robust neural fuzzy control of uncertain systems: A Lyapunov theory approach

The objective of this research was to develop effective control strategies for uncertain nonlinear dynamical systems. In the first stage of the research, neural fuzzy controllers were proposed. Genetic algorithms were employed to design and fine-tune the proposed neural fuzzy controllers, which then were tested on an anti-lock brake system model and a ground vehicle. Training or fine-tuning of the above described controllers was performed off-line and found to be time consuming. To overcome this problem, an adaptive control algorithm was developed that learns and compensates for the unmodeled dynamics of the plant online. In addition, a robustifying component was proposed whose role is to suppress modeling errors and uncertainties. Integrating the adaptive and the robust approaches resulted in a guaranteed transient tracking performance and a guaranteed final tracking error accuracy in the presence of modeling errors and disturbances. The closed-loop system driven by the proposed controllers was shown, using the Lyapunov method, to be stable with all the adaptation parameters being bounded. To further enhance the performance of the proposed control strategies, a self-organizing raised-cosine radial basis functions (RCRBFs) component was included in the control architecture. The proposed self-organizing RCRBF network can adjust its size by growing or shrinking the number of basis functions used according to the design specification. Performance comparison of the proposed controllers with the one in the literature was conducted. The proposed controller outperformed the controllers found in the literature

Analytical Performance of the Sysmex HISCL HBsAg Assay and Comparison with the Roche Elecsys HBsAg II Quant Assay in the Quantification of Hepatitis B Surface Antigen

Background and Objectives: This study aims to estimate the analytical performance of the Sysmex HISCL HBsAg assay and to assess the analytical correlation with the Roche Elecsys HBsAg II quant assay with clinical samples and the WHO International Standard (IS). Materials and Methods: The intra-assay precision, linearity, assay limitation, accuracy, and comparative evaluation of the HISCL HBsAg assay were estimated. Results: Extrapolating from the plot of the average total allowable error versus the reference value, an accuracy goal of 20% would be achieved around a limit of quantification (LoQ) of 0.014867 IU/mL. The percentage of biases for each level of the WHO IS measured by the two assays were less than 15%, except for the WHO 3rd IS, for which the HISCL HBsAg assay achieved a percentage of bias of 33%. In the comparative evaluation, Passing–Bablok regression analysis did not reveal any significant deviation from linearity between the two assays (y = −48.6998 + 1.9206x; p = 0.79 by the CUSUM test for linearity). The mean difference of the quantitative HBsAg level between the two assays was 1762.5 IU/mL in the Bland–Altman plot. Conclusions: The HISCL HBsAg assay, with a highly sensitive LoQ of 0.03 IU/mL, showed similar analytical performance in HBsAg quantification to the Elecsys HBsAg II quant assay and may be helpful in obtaining better diagnoses and therapeutic strategies for treating HBV infections

Fuzzy Adaptive Robust Control of a Class of Nonlinear 1 Systems

Fuzzy adaptive robust tracking controller for a class of uncertain nonlinear dynamical systems is proposed and analyzed. The controller's construction and its analy-sis involve sliding modes. The proposed controller con-sists of two components. Robust feedback component is employed to eliminate the effects of disturbances, while a fuzzy logic component equipped with an adap-tation mechanism reduces modeling uncertainties by approximating model's nonlinearities on-line. Projec-tion method is used to prevent the adaptation param-eters from going unbounded in the presence of distur-bances. It is shown that the closed-loop system driven by the proposed controller is stable and the adapta-tion parameters are bounded. A guaranteed transient performance and a guaranteed final tracking accuracy in the presence of parametric uncertainties and distur-bances are achieved. Furthermore, if there are no dis-turbances and the unknown model's nonlinearities are within the approximation range of the fuzzy logic sys-tem, asymptotic output tracking is also achieved.

Outward currents of single hippocampal cells obtained from the adult guinea-pig.

1. Neurones were isolated from the hippocampus of adult guinea-pigs by enzymatic and mechanical treatment. The electrophysiological properties of these cells were examined immediately after dissociation by intracellular recordings using low-resistance electrodes (2-5 M omega). 2. Pyramidal-shaped cells were identified visually. Intracellular recordings showed that these cells have input resistances ranging from 200 to 1300 M omega. Passive voltage responses to hyperpolarizing current injection were fitted by single exponentials decaying with time constants ranging from 15 to 60 ms. This suggests that the electrotonic structure of these cells is compact such that injected current elicited isopotential intracellular responses. 3. Outward currents activated by depolarization were examined in these cells using voltage-clamp techniques. The amplitude and the time course of the outward currents were profoundly affected by the holding potential. For cells held at -50 mV or more positive, depolarizing steps produced a slowly rising outward current. At holding potentials negative to -55 mV depolarizing pulses produced an additional early transient outward current followed by a slowly rising component which decayed gradually during sustained depolarizations. 4. The outward currents were separated by their kinetic properties and their sensitivity to cobalt (Co2+), tetraethylammonium (TEA) and 4-aminopyridine (4-AP). 5. The transient current peaked within 6 ms of the onset of depolarizing pulses. It decayed exponentially with a time constant of 20-40 ms. The amplitude of the current activated by a fixed depolarization increased gradually as the duration or the amplitude of the hyperpolarizing pre-pulse increased. The current activated by a fixed depolarization reached its half-maximal level when the hyperpolarizing pre-pulse was at -83 mV. 6. 4-AP exerted two actions on the transient current. Firstly, the time constant of the falling phase decreased by about a factor of two. Secondly, the current was blocked in a time- and voltage-dependent manner: the block increased when the hyperpolarizing pre-pulse lengthened. TEA, up to 10 mM, did not affect the amplitude of the transient current. Co2+ suppressed this current. The effects of Co2+ consisted of a shift to the positive direction of the voltage dependence of the current. 7. The delayed currents can be divided into Ca2+-dependent and Ca2+-independent components. The component persistent in the Co2+ solution (K-current) decayed slowly with maintained depolarization (time constant greater than 3 s).(ABSTRACT TRUNCATED AT 400 WORDS