ROBOTS CONTROL BY ADAPTIVE GAIN SMOOTH SLIDING OBSERVER-CONTROLLER AND PARAMETER IDENTIFICATION

An adaptive gain, smooth sliding observer-controller are developed to control uncertain parameters, -degree of freedom rigid robotic manipulators. Furthermore, an on-line, closed loop identification scheme, for time-varying parameters is proposed in order to obtain useful information despite loads, external disturbances and faults detection. In order to reduce the chattering, a smooth switching function (parameterised tangent hyperbolic function) is used instead of pure relay one, into the observer and the controller. The gains of the switching functions are adaptively updated, depending on the estimation error and tracking error, respectively. By using adaptive gains, the transient and tracking responses are improved. Simulation results with a two degree of freedom (DOF) robot manipulator are presented to show the interest of the approach

Flexible Joints Robotic Manipulator Control By Adaptive Gain Smooth Sliding Observer-Controller

An adaptive gain sliding observer for uncertain parameter nonlinear systems together with an adaptive gain sliding controller is proposed in this paper. It considered nonlinear, SISO affine systems, with uncertainties in steady-state functions and parameters. A further parameter term, adaptively updated, has been introduced in steady state space model of the controlled system, in order to obtain useful information despite fault detection and isolation. By using of the sliding observer with adaptive gain, the robustness to uncertainties is increased and the parameters adaptively updated can provide useful information in fault detection. Also, the state estimation error is bounded accordingly with bound limits of the uncertainties. The both of them, the sliding adaptive observer and sliding controller are designed to fulfill the attractiveness condition of its corresponding switching surface. An application to a single arm with flexible joint robot is presented. In order to alleviate chattering, a parameterized tangent hyperbolic has been used as switching function, instead of pure relay one, to the observer and the controller. Also, the gains of the switching functions, to the sliding observer and sliding controller are adaptively updated depending of estimation error and tracking error, respectively. By the using adaptive gains, the transient and tracking response can be improved

Influence of the lattice topography on a three-dimensional, controllable Brownian motor

We study the influence of the lattice topography and the coupling between motion in different directions, for a three-dimensional Brownian motor based on cold atoms in a double optical lattice. Due to controllable relative spatial phases between the lattices, our Brownian motor can induce drifts in arbitrary directions. Since the lattices couple the different directions, the relation between the phase shifts and the directionality of the induced drift is non trivial. Here is therefore this relation investigated experimentally by systematically varying the relative spatial phase in two dimensions, while monitoring the vertically induced drift and the temperature. A relative spatial phase range of 2pi x 2pi is covered. We show that a drift, controllable both in speed and direction, can be achieved, by varying the phase both parallel and perpendicular to the direction of the measured induced drift. The experimental results are qualitatively reproduced by numerical simulations of a simplified, classical model of the system

Sodium-Glucose Cotransporter 2 Inhibitors and Kidney Outcomes:True Renoprotection, Loss of Muscle Mass or Both?

Inhibitors of sodium-glucose cotransporter 2 (SGLT2) have emerged as practice-changing treatments for patients with type 2 diabetes, reducing both the risk of cardiovascular events and kidney events. However, regarding the latter, caution is warranted, as these kidney endpoints are defined using glomerular filtration rate estimations based on creatinine, the non-enzymatic product of creatine residing in muscles. Creatinine-based estimations of the glomerular filtration rate are only valid if the treatment has no effect on changes in muscle mass over time. Yet, circumstantial evidence suggests that treatment with SGLT2 inhibitors does result in a loss of muscle mass, rendering serum creatinine-based kidney endpoints invalid. Currently, it cannot be excluded that the described renoprotective effect of SGLT2 inhibitors is in part or in whole the consequence of a loss of muscle mass. Post-hoc analyses of existing trials or new trials based on kidney function markers independent of muscle mass can provide more definitive answers on the proposed renoprotective effects of SGLT2 inhibitors

Leptoquark pair production at the Fermilab Tevatron: Signal and backgrounds

We perform a Monte-Carlo simulation of scalar leptoquark pair production at the Tevatron (energy =1.8 TeV and luminosity =100 pb^{-1}) with ISAJET. We also investigate the dominant sources of Standard Model background: Z*jj, ZZ production and heavy quark top-antitop. We find that the top-antitop background is the most important except near the Z pole where the Z*jj background is peaked. We also evaluate the signal-to-background ratio and find a discovery reach of 130 GeV (170 GeV) for a branching ratio of B(LQ-> eq)=0.5 (B=1).Comment: 8 pages, 6 figures, latex (revtex

Field-angle dependence of sound velocity in the Weyl semimetal TaAs

The elastic modulus $c_{44}$ of a single crystal of the Weyl semimetal TaAs was investigated by measuring relative changes in the sound velocity under application of a magnetic field up to 10 T. Using an ultrasonic pulsed-echo technique, we studied the shear response of the crystal when the angle between the sound wave propagation and the magnetic field is changed. We observe a broken tetragonal symmetry at fields above 6 T, an anisotropy that is likely related to a longitudinal negative magnetoresistance and therefore might provide evidence of the chiral anomaly, one of the main topological signatures of this class of materials. We also observe quantum oscillations in the sound velocity whose frequencies vary with magnetic field orientation. A fan diagram of Landau level indices reveals topological and trivial Berry phases, depending on the field orientation, indicating a sensitivity to different Fermi surface pockets that do or do not enclose Weyl nodes respectively

Demonstration of a controllable three-dimensional Brownian motor in symmetric potentials

We demonstrate a Brownian motor, based on cold atoms in optical lattices, where isotropic random fluctuations are rectified in order to induce controlled atomic motion in arbitrary directions. In contrast to earlier demonstrations of ratchet effects, our Brownian motor operates in potentials that are spatially and temporally symmetric, but where spatiotemporal symmetry is broken by a phase shift between the potentials and asymmetric transfer rates between them. The Brownian motor is demonstrated in three dimensions and the noise-induced drift is controllable in our system.Comment: 5 pages, 4 figure