In this article, we propose optimal discretization of analog filters (or controllers) based on the theory of sampleddata H∞ control. We formulate the discretization problem as minimization of the H∞ norm of the error system between a (delayed) target analog filter and a digital system including an ideal sampler, a zero-order hold, and a digital filter. The problem is reduced to discrete-time H∞...

The conjecture that dark matter in galaxies is mostly cold fractal gas exposed in another paper at this conference is developed in the more general context of the thermodynamics of the ideal isothermal gas subject to gravitational instability. This simple gas model already contains the contrary ingredients able to prevent an asymptotic equilibrium: any growing gravothermal singularity evaporate...

INTRODUCTION Bubble columns are widely used in industrial gas-liquid operations (e.g. gas-liquid reactions, fermentations) in chemical and biochemical processes industries, due to their simple construction, low operating cost and high-energy efficiency. In all these processes, gas hold-up and bubble size are important design parameters since they define the gasliquid interfacial area available ...

Abstract: In this paper, the zero-order-hold (ZOH) discretization of higher-order sliding mode control (SMC) systems is studied. The equivalent control based SMC systems with relative degree higher than one is first formulated into a canonical form which is easy for control design. Theoretical results for the ZOH-discretized SMC systems with relative degree higher than one are given, including ...

This paper is concerned with the analyses of multi-rate controllers, which update the controller output faster than the measurement sampling frequency by a factor of N. The controlled systems is continuous, and the discrete time controller is obtained as its zero order hold equivalent. After deriving a set of equations necessary for analysis and design of multi-rate systems, the open loop chara...

-In this paper, we consider a general linear interconnection of a continuous-time plant and a discretetime controller via sample and hold devices. When the closed loop sampled-data feedback system is internally stable, bounded inputs produce bounded outputs. We present some explicit formulae for the induced norm of the closed loop system with ~ (i.e. peak value) and ~1 (i.e. integral absolute) ...

Texas contains a rich but still poorly known cavernicole fauna. Approximately 1,040 terrestrial and 150 aquatic species have been recorded from the state. This number will doubtless greatly increase when large collections, especially of mites, centipedes, and miscellaneous insects, are identified and described. An estimated 81 aquatic and 161 terrestrial species are believed to be sufficiently ...

An important problem in the field of force-reflecting systems and telerobotics is poor rendering of contact, particularly of contact with stiff surfaces. There are numerous possible sources of poor performance, including poor contact models, sampling errors, and delays due to computation or data transmission. In this paper we examine effects due to sample-and-hold, which is a fundamental proper...