27,988 research outputs found
PI output feedback control of differential linear repetitive processes
Repetitive processes are characterized by a series of sweeps, termed passes, through a set of dynamics defined over a finite duration known as the pass length. On each pass an output, termed the pass profile, is produced which acts as a forcing function on, and hence contributes to, the dynamics of the next pass profile. This can lead to oscillations which increase in amplitude in the pass-to-pass direction and cannot be controlled by standard control laws. Here we give new results on the design of physically based control laws. These are for the sub-class of so-called differential linear repetitive processes which arise in applications areas such as iterative learning control. They show how a form of proportional-integral (PI) control based only on process outputs can be designed to give stability plus performance and disturbance rejection
On the Development of SCILAB Compatible Software for the Analysis and Control of Repetitive Processes
In this paper further results on the development of a SCILAB compatible software package for the analysis and control of repetitive processes is described. The core of the package consists of a simulation tool which enables the user to inspect the response of a given example to an input, design a control law for stability and/or performance, and also simulate the response of a controlled process to a specified reference signal
LMI based Stability and Stabilization of Second-order Linear Repetitive Processes
This paper develops new results on the stability and control of a class of linear repetitive processes described by a second-order matrix discrete or differential equation. These are developed by transformation of the secondorder dynamics to those of an equivalent first-order descriptor state-space model, thus avoiding the need to invert a possibly ill-conditioned leading coefficient matrix in the original model
Radiation environment for rendezvous and docking with nuclear rockets
Radiation environment data for the NERVA engine are provided which may be utilized in estimating radiation exposures associated with various space maneuvers. Spatial distributions of neutron and gamma tissue kerma rates produced during full thrust operation of the engine are presented. Final rendezvous with an orbiting space station would be achieved subsequent to full thrust operation during a period of 10 or more hours duration in which impulse is delivered by the propellant used for removal of decay heat. Consequently, post operation radiation levels are of prime importance in estimating space station exposures. Maps of gamma kerma rates around the engine are provided for decay times of 4 and 24 hours after a representative firing. Typical decay curves illustrating the dependence of post operation kerma rates on decay time and operating history are included. Examples of the kerma distributions around the engine which result from integration over specific exposure periods are shown
Central Charge and the Andrews-Bailey Construction
From the equivalence of the bosonic and fermionic representations of
finitized characters in conformal field theory, one can extract mathematical
objects known as Bailey pairs. Recently Berkovich, McCoy and Schilling have
constructed a `generalized' character formula depending on two parameters \ra
and , using the Bailey pairs of the unitary model . By taking
appropriate limits of these parameters, they were able to obtain the characters
of model , model , and the unitary model with
central charge . In this letter we computed the effective
central charge associated with this `generalized' character formula using a
saddle point method. The result is a simple expression in dilogarithms which
interpolates between the central charges of these unitary models.Comment: Latex2e, requires cite.sty package, 13 pages. Additional footnote,
citation and reference
On the Control of Distributed Parameter Systems using a Multidimensional Systems Setting
The unique characteristic of a repetitive process is a series of sweeps, termed passes, through a set of dynamics defined over a finite duration with resetting before the start of the each new one. On each pass an output, termed the pass profile is produced which acts as a forcing function on, and hence contributes to, the dynamics of the next pass profile. This leads to the possibility that the output, i.e. the sequence of pass profiles, will contain oscillations which increase in amplitude in the pass-to-pass direction. Such behavior cannot be controlled by standard linear systems approach and instead they must be treated as a multidimensional system, i.e. information propagation in more than one independent direction. Physical examples of such processes include long-wall coal cutting and metal rolling. In this paper, stability analysis and control systems design algorithms are developed for a model where a plane, or rectangle, of information is propagated in the passto- pass direction. The possible use of these in the control of distributed parameter systems is then described using a fourthorder wavefront equation
Production of a water quality map of Saginaw Bay by computer processing of LANDSAT-2 data
Surface truth and LANDSAT measurements collected July 31, 1975, for Saginaw Bay were used to demonstrate a technique for producing a color coded water quality map. On this map, color was used as a code to quantify five discrete ranges in the following water quality parameters: (1) temperature, (2) Secchi depth, (3) chloride, (4) conductivity, (5) total Kjeldahl nitrogen, (6) total phosphorous, (7)chlorophyll a, (8) total solids and (9) suspended solids. The LANDSAT and water quality relationship was established through the use of a set of linear regression equations where the water quality parameters are the dependent variables and LANDSAT measurements are the independent variables. Although the procedure is scene and surface truth dependent, it provides both a basis for extrapolating water quality parameters from point samples to unsampled areas and a synoptic view of water mass boundaries over the 3000 sq. km bay area made from one day's ship data that is superior, in many ways, to the traditional machine contoured maps made from three day's ship data
Old and New Fields on Super Riemann Surfaces
The ``new fields" or ``superconformal functions" on super Riemann
surfaces introduced recently by Rogers and Langer are shown to coincide with
the Abelian differentials (plus constants), viewed as a subset of the functions
on the associated super Riemann surface. We confirm that, as originally
defined, they do not form a super vector space.Comment: 9 pages, LaTex. Published version: minor changes for clarity, two new
reference
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